Notes Lab #1: PHYSICAL PROPERTIES OF MINERALS
Earth Lab Chapter 2
Crystal Form/Crystal Habit – the external geometric shape of a crystal which reflects its atomic structure. Luster – how light is reflected from a fresh surface of a mineral, e.g. metallic, sub-metallic, nonmetallic. Hardness – the resistance to abrasion on a fresh surface. Can it be scratched? See MOHS Hardness Scale’s 10 index minerals (Pg 31, Table 2.3 Earth Lab): Talc is #1 and Diamond is # 10. The first two minerals, Talc and Gypsum, can be scratched with a fingernail. Minerals harder than 6 are harder than a porcelain streak plate (won’t streak). Streak – color of a powdered mineral which is tested by rubbing the mineral across a porcelain streak plate. Color – hue, tint or actual color of a mineral. Not generally diagnostic for minerals, e.g. quartz may be colorless, milky, pink, purple, smoky, etc. Cleavage – the tendency to break along preferred surfaces called cleavage planes. Cleavage planes present flat, light reflective surfaces (surfaces cut with a rock saw are dull). Fracture – the tendency to break along an irregular surface. May appear hackly (rough) or conchoidal (curved and ribbed). Specific Gravity – density. Note high specific gravity of galena, magnetite, pyrite. Effervescence – Acid, such as hydrochloric acid (HCl), applied to CaCO3 causes a “fizzing” reaction. 2H + CO3 → H2O + CO2 (fr om HCl) (from CaCO3) (water) (escaping gas bubbles) Magnetic – attracted by a magnet. Taste – unique flavor: halite tastes like salt. Smell – distinctive odor: sulfurous smell of galena. Feel – distinct physical sensation when touched: silky (talc); greasy (graphite). Double Refraction – ray of light splits in two producing two offset images (Iceland spar calcite). Tenacity – resistance to mechanical deformation (breaking, bending). Some examples: • Brittle - describes most minerals • copper is ductile – can be elongated into wire • gold is malleable – can be shaped and pounded into a thin leaf. Fluorescence – short light waves radiate back as long waves; changes the color of some minerals. _______________________________________________________________________________________________________________
Physical properties of minerals: Mineralogy Society of America Website http://www.minsocam.org/MSA/collectors_corner/id/mineral_id_keyi3.htm Other minerals websites: http://webmineral.com/determin.shtml http://csmres.jmu.edu/geollab/Fichter/Minerals/Minalpha.html http://pubs.usgs.gov/gip/gemstones/
Notes Lab #2: ROCK FORMING MINERALS Major elements in the Earth’s Crust: O Si 75%
oxygen silica
Al Fe Ca Na K Mg
aluminum iron calcium sodium potassium magnesium
All others
23%
Earth Lab Chapter 3
2% 100%
Rock Cycle – the events involving the formation, alteration, destruction and re-formation of the three rock types: igneous, metamorphic, and sedimentary rocks. Geologic processes convert each type of rock into the other two types. Plate tectonics and climate drive the rock cycle processes. The Silicate Ion - the basic building block of all silicate mineral structures. It is a tetrahedron: a pyramidal structure with a central silicon ion (si4+) surrounded by four oxygen ions (O2-), giving the formula SiO4 4- . Because the silicate ion has a negative charge, it often bonds to cations to form electrically neutral minerals. The silicate ion typically bonds with cations such as sodium (Na+), potassium (K+), calcium (Ca+), magnesium (Mg++), and iron (Fe++). Chemical Classification Groups of the Rock Forming Minerals: 1. Silicates - basic chemical building block is the silica tetrahedron (SiO4 ) 2. Non-Silicates: Example: a. Carbonates - Basic unit is CO3…………… calcite CaCO3 b. Sulfates Basic unit is SO4…………… gypsum CaSO4 · 2H2O c. Sulfides S plus a metal(s) …………… galena PbS d. Oxides O plus a metal(s)……………. magnetite Fe3O4 e. Hydroxides - OH plus a metal(s)………….. limonite FeO · OH · nH2O f. Phosphates - Basic unit is PO4 …………… apatite Ca5(PO4)3(F,C.,OH) g. Halides Halogen ion present ……...... halite NaCl h. Native elements - Occur in elemental form: Ag silver Cu copper Au gold Fe iron Pt platinum C graphite, diamond S sulfur Feldspars - The most abundant group of minerals in the crust. They are framework silicates; however, aluminum has substituted for some of the silicon. In addition to silicon, oxygen, and aluminum the feldspars contain sodium, calcium, or potassium. Feldspars containing potassium are called potassium feldspars or K feldspars (Two K feldspars are microcline and orthoclase). If sodium or calcium, or both, are incorporated into the feldspar crystal structure, then the mineral is plagioclase feldspar.
K Orthoclase; Microcline
Na
Plagioclase
feldspars
Ca
A website for the feldspar minerals: http://www.minerals.net/mineral/silicate/tecto/feldspar/feldspar.htm
Notes Lab #3: IGNEOUS ROCKS
Earth Lab Chapter 4
Rock Identification The elements present in the Earth are organized into mineral grains, and mineral grains aggregate to form rocks. In lab you learned to identify common rock forming minerals by their physical properties, now you will learn to recognize common rocks. Rocks are mixtures of minerals, held together by relatively weak bonds between individual mineral grains or, in some cases, by cementing materials which act like glue. Classification of rocks is based on the way the mineral grains of the rock crystallize. Igneous rocks are formed by solidification of magma (freezing) or by accumulation of fragments ejected during volcanic eruptions. Sedimentary rocks are formed by the deposition and subsequent aggregation of rock or mineral fragments produced by erosion and transported by wind or water. Some sedimentary rocks form by precipitation of minerals from the dissolved elements present, primarily, in seawater. Metamorphic rocks are formed when existing sedimentary or igneous rocks are subjected to increases in temperature, pressure, or stress, which cause the original mineral grains to recrystallize or be replaced by new minerals, stable under the new conditions.
Igneous Rocks Igneous rocks are composed of hard minerals (H ≥ 6), mostly silicates. Feldspar is the most common igneous mineral. Biotite (and occasionally muscovite) is the only soft mineral. Other igneous minerals include quartz, hornblende, olivine, and pyroxene. Igneous Rock ID - classified by color/composition and grain size/texture. When magma freezes quickly in extrusive (volcanic) environments, crystals grow rapidly from many nuclei, resulting in a very fine-grained (grains too small to see) rock. When magma cools below the surface (intrusive environment) heat is lost slowly and fewer nuclei develop, so the rock is more coarsegrained. COMPOSITION (related to color and amount of silica) (a) Felsic – light color, high amount of silica (70%); rich in K-feldspar and quartz. (b) Intermediate – medium color, medium amount of silica (60%). (c) Mafic – dark color, Fe & Mg content equal to silica (50%); minerals: olivine, pyroxene, amphibole, biotite, and plagioclase feldspar. (d) Ultramafic – dark greenish, more Fe & Mg than silica (40%); composed mainly of olivine and pyroxene. An ultramafic rock is almost always coarse grained and is called a peridotite. GRAIN SIZE (Igneous Textures): (a) Coarse (phaneritic) – crystal grains are visible to the eye, slow cooling within Earth produces large grains. Found in plutonic or intrusive igneous rocks. (b) Fine (aphanitic) – crystal grains not visible to unaided eye, fast cooling on Earth’s surface. Found in volcanic or extrusive igneous rocks.
(c) (d) (e)
Glassy (hyaline) – non-crystalline, very fast cooling, volcanic, extrusive. Glasses are said to be amorphous because they have no crystal structure, e.g. obsidian Vesicular (abundant gas vesicles) – frothy glass, very fast cooling, volcanic, extrusive, e.g. scoria, pumice. Porphyritic - coarse-grained crystals and fine-grained crystals in the same rock. • Phenocrysts are the large crystals in the finer-grained rock matrix. The two crystal sizes indicate both slow and fast cooling rates; therefore, there are both plutonic and volcanic (intrusive and extrusive) constituents of the same rock.
GRAIN SHAPE: Euhedral – well formed crystals Subhedral – partially well formed crystals Anhedral – poorly formed crystals Specific rock names depend on how felsic or mafic a rock is and whether it is fine or coarse grained. The compositional variable is determined by the ratio of plagioclase feldspar to potassium feldspar, or more simply, by the amount and type of mafic minerals. Use Table 4.3, page 71 in Earth Lab as a guide to igneous rock identification/nomenclature. Magma - molten rock originates at high temperature 20-100 miles deep in the upper mantle or lower crust. Rocks are solid under pressure; it takes high temperature to melt rocks. Earthquakes release the confining pressure, rocks liquefy and start rising toward the surface because the magma is lighter than the surrounding rock. Geothermal Gradient- the temperature of the earth increases an average of 25 degrees Celsius per kilometer of depth in normal continental crust A website with pictures of igneous rocks and a guide to classification: http://csmres.jmu.edu/geollab/Fichter/IgnRx/IgAlphabetical.html http://csmres.jmu.edu/geollab/Fichter/IgnRx/simpclass.html
Notes For Lab #4: SEDIMENTARY ROCKS
Earth Lab Chapter 5
Sedimentary Rock layers cover Earth’s surface along coastlines, deltas, bars, reefs, continental margins, ocean floors, inland seas, rivers, deserts, glaciers, and paleo-sedimentary environments. Principle of Original Horizontality – Sediments are deposited as horizontal beds. Principle of Superposition - Each layer of sedimentary rock in a tectonically undisturbed sequence is younger than the layer beneath it and older than the layer above it. Sedimentary Rock Mineralogy – quartz, calcite, clay minerals, rock fragments, halite, gypsum, feldspars, micas, etc. (stable at surface temperatures and pressure). Sedimentary rocks are aggregates of transported particles that were deposited in a basin (sea, ocean, lake) or form as a chemical precipitate from an aqueous environment. Fossils may be present. CLASSIFICATION of Sedimentary Rocks • Clastic – broken fragments of pre-existing rocks lithify to form a clastic sedimentary rock, e.g. shale, siltstone, sandstone, breccia, conglomerate. Rock nomenclature/identification is based on grain size. See Table 5.3 on page 86 of the Lab Manual Clastic sedimentary rocks are composed primarily of quartz, feldspar, and clay minerals. Dark minerals are rare. Conspicuous layering or bedding may be present. •
Chemical – crystals are formed from chemical evaporation or precipitation. Rock nomenclature/identification is based on chemical or mineralogical composition, e.g. limestone (calcite); chert (quartz); rock salt (halite); gypsum, etc. See Table 5.5 on page 89.
•
Biogenic – derived from altered animal (coralline limestone; bryozoan limestone; chalk, etc.) or plant remains (coal). Also called skeletal or fossiliferous sedimentary rocks. See Figures 5.17-5.20 on pages 90-91.
Processes producing Sedimentary Rocks: weathering, erosion, deposition and lithification. PHYSICAL WEATHERING: frost wedging, isostatic rebound, plant growth, or man mechanically breakdown rocks. Quartz will eventually physically weather to sand size particles (no smaller). CHEMICAL WEATHERING: dissolution by groundwater, oxidation, or hydration. Silicate minerals weather chemically to form clay; however, quartz resists chemical weathering. EROSION –the wearing away, removal, and transport of Earth materials by wind, glaciers, gravity, or water. DEPOSITION – loose, unconsolidated grains come to rest in a basin or depression. LITHIFICATION – the process of rock formation: sediments are changed into solid rock (lithified) by compaction, cementation and/or recrystallization. TEXTURE – size, shape and arrangement of mineral components/grains. • SIZE – ranges from very fine (clay) to very coarse (boulder). A boulder is at least the size of a volley ball. See Table 5.3 on page 86 of the Lab Manual. • SHAPE – Rounded: grains have traveled far from the source rock, e.g. conglomerate.
Angular: grains did NOT travel far from source rock, e.g. sedimentary breccia. BEDDING – arrangement of sedimentary rocks in layers due to gravity • parallel bedding • graded bedding • cross bedding • compositional banding SORTING – grains are separated by particle size (clay, silt, sand, granule/gravel, pebble, cobble). Well Sorted - grains are nearly all the same size. Poorly Sorted - means grains are different sizes.
http://csmres.jmu.edu/geollab/Fichter/SedRx/Sedalphab.html http://csmres.jmu.edu/geollab/Fichter/SedRx/basickey.html
Notes for Lab #5:
METAMORPHIC ROCKS
Earth Lab Chapter 6
Metamorphic Rocks are derived from pre-existing rocks by mineralogical, chemical, and/or structural changes in the solid state in response to changes in temperature, pressure, and deformation at depth in the Earth’s crust. Types of Metamorphism: CONTACT METAMORPHISM (a.k.a. thermal metamorphism) – Metamorphism resulting from the heating of rock near a magmatic intrusion. Contact metamorphic rocks are usually fine grained and non-foliated (do not contain flat minerals displaying alignment). Hornfels and marble are two contact metamorphic rocks. See Figure 6.8 on plate 108 of the lab manual. REGIONAL METAMORPHISIM – Metamorphism affecting an extensive area where directed pressure combines with high temperatures and confining pressures (10-30 km deep, lower half of crust). Wide scale metamorphism is related to tectonic processes, common at convergent plate boundaries. • Confining Pressure increases approximately 300 atm/km of depth. Rock volume decreases as confining pressure increases. • Temperature increases an average of 25 º C/km of depth. • Directed Pressure – forces on rock are not equal in all directions (differential stress). • Foliation – flattening of rock/minerals perpendicular to the directed pressure • Minerals are stable under a specific range of pressure and temperature (see the Barrovian Series - metamorphic rocks derived from shale). CLASSIFICATION OF METAMORPHIC ROCKS: Foliated Rocks and Non- Foliated Rocks. See Tables 6.5 & 6.6, pages 113-14 in Earth Lab. FOLIATED ROCKS – A planar texture / alignment of platy (flat) minerals due to directed pressure. • Slaty cleavage – Rock: Slate – fine grained rock • Phyllitic cleavage – Rock: Phyllite – fine to medium grained with mica sheen • Schistosity – Rock: Schist – medium grained, shows rock cleavage or schistosity • Gneissic Banding – Rock: Gneiss – coarse grained with gneissic color banding caused by successive layers of light and dark minerals; recrystallization is extensive. NON-FOLIATED ROCKS - identified by mineral content, usually monomineralic (one mineral). Absence of platy (flat) minerals and planar or laminated texture. 1. Massive Texture – Fine grained non-foliated rock, e.g. serpentinite 2. Granoblastic Texture – coarse grained non-foliated rock, e.g. quartzite, marble A website with pictures of Metamorphic Rocks: http://csmres.jmu.edu/geollab/Fichter/MetaRx/Metaalphab.html
Notes for Lab #6: Introduction to Maps
Earth Lab Chapter 1
Topographic Maps – contour lines indicate the shape of the land surface. Political boundaries, rivers, towns, roads, etc. are also mapped. See Lab #8. Bathymetric Maps – depict the depth and physiographic features (trenches, ridges, seamounts, and plains) of the ocean floor. See Labs #8 and #10. Geologic Maps – depict the distribution of rock bodies and the various kinds of folds, faults, and unconformities exposed on the land surface. The different rock bodies are represented by colors and/or patterns with letter codes: the first letter, uppercase, for a sedimentary formation indicates the geologic period in which the formation was deposited; subsequent letters in lowercase are an abbreviation of the formation name. The map legend is a series of boxes arranged from oldest at the bottom to youngest at the top. Legend boxes are color/pattern coded. See Lab #9. Satellite Images - NASA’s EOS (Earth Observing System) and Landsat.
True North – The northern end of Earth’s axis of rotation; the geographic North Pole. Modern convention has it that the top of a map is map north, unless otherwise indicated. A map legend usually includes a north arrow. Magnetic North – The direction a compass or magnetized needle points. The magnetic North Pole is separated from the geographic North Pole by more than 1,000 miles. If we draw lines from a particular location to both the geographic and the magnetic north poles an angle forms: the Angle of Declination. The size of the angle varies depending on our location on Earth. In some locals this angle is zero, meaning that the two poles are on the same line. The zero declination line travels offshore down the west coast of Florida; that means that locations in Florida have a very small angle of declination. The angle of declination in Miami is ± 5 degrees east (of true north). A good compass can be adjusted so that magnetic north will coincide with
true north (map north). Degrees are subtracted from an east declination; degrees are added to a west declination. Compass Points:
North NNE NE East ESE SE
0º 22.5º 45° 90° 112.5º 135º
South SSW SW West WNW NW
180° 202.5º 225º 270º 292.5º 315°
Bearing – The clockwise angle between true north and the direction to a particular target on a map. It is a travel direction expressed in degrees. For example, if you travel from FIU on a NE bearing you will intersect MIA. Latitude- A measurement of location north or south of the Equator (measures a given point in terms of its angular distance from the Equator). The Equator is a great circle that divides Earth into Northern and Southern Hemispheres. The Equator is 0° of latitude. The Poles are 90º of latitude. Latitudes north of the equator are designated N; those south of the equator are designated S. Lines of latitude are also called parallels (parallels of latitude). Longitude – The lines running north and south from pole to pole are lines of longitude (meridians of longitude). The Prime Meridian, Longitude 0°, goes through Greenwich, England (Greenwich is a section of London). The reference meridian on the globe 180 ºfrom Greenwich is the International Dateline. Locations east of Greenwich heading toward the International Dateline are East Longitude; locations west of Greenwich are West Longitude. • When giving Latitude and Longitude coordinates. Latitude is first: Miami’s coordinates are: 25° 47' N latitude; 80° 13' W longitude. • One degree of longitude or latitude is divided into 60 ′ (minutes); a minute is divided into 60" (seconds). Map Projection – A system for displaying the curved surface of the geographic grid on a flat surface. Geographic Grid – method for describing locations on the earth’s curved surface. The grid is divided into imaginary circles perpendicular to the axis of rotation (latitude) and parallel to the axis of rotation (longitude). Township and Range System – based on a grid. In Florida the baseline (east-west reference line) and principle meridian (north-south reference line) intersect at the State capital in Tallahassee. The Tallahassee Meridian is the name of the reference north-south line. Each square mile in Florida has a Township and Range System address used in legal descriptions, city planning, real estate transactions, oil leases, flood maps, etc. • •
Range lines: the north-south township boundary lines are drawn every 6 miles East or West of Tallahassee. Township lines: the east-west township boundaries lines are drawn every 6 miles North or South of Tallahassee.
•
•
Townships: The grid of range and township lines has a spacing of 6 miles (36 square miles); the resulting square is called a township ( Not all townships are exactly square. Every few rows of townships will have a slight "jog" in the meridians to compensate for the curvature of the earth). Sections: Each township is divided into 36 sections. Each section is one mile square and contains 640 acres. The sections are numbered from 1 to 36 in a snaking order: Section 1 is in the upper right corner and Section 36 is in the lower right corner of the section.
A property on the southeast corner of SW 112th Avenue and N. Kendall Drive is located in: T 56S – R 39E – Section 06 (It is 56 townships south of Tallahassee; 39 townships east of Tallahassee. Section 06 means it is in the upper left corner of the township). A property in Key West is located in T 66 S –R 29 E – Section 26 A property in the Florida Panhandle is located in T 3 N – R 33 W – Section 15 Map Scale: http://mac.usgs.gov/mac/isb/pubs/factsheets/fs01502.html Land System in FL: http://www.geocities.com/Heartland/Bluffs/3010/landsyst.htm Free Maps: http://www.geographynetwork.com/freeresources.html What is GIS: http://www.gis.com/whatisgis/index.html GIS: http://erg.usgs.gov/isb/pubs/gis_poster/ NASA’s EOS and Landsat 7: http://eospso.gsfc.nasa.gov/ftp_docs/Landsat7_writer_guide.pdf Landsat Images: http://landsat.gsfc.nasa.gov/earthasart/ NASA’s Interactive Global Hydrology & Climate Center http://www.ghcc.msfc.nasa.gov/GOES/ Landforms from space: http://daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/GEO_COMPLETE_TOC.html Longitude & Latitude: http://www-istp.gsfc.nasa.gov/stargaze/Slatlong.htm
Notes for Lab #7: TOPOGRAPHIC MAPS
Earth Lab Chapter 11
Geomorphology - the branch of geology that studies landforms, their origin and reshaping over time. Topography – the shape of the physical features of the land surface area. Topographic Map – represents the actual topography of a given area in 2-
dimensions.
Contour Lines – (1) continuous lines of (2) equal elevation (3) that never divide or intersect and are (4) at right angles to the slope. • Closely Spaced Lines – depict steep terrain. Widely Spaced Lines – depict terrain that is almost flat or has a gentle slope. • Hills – depicted by concentric, continuous loop contour lines. • Depressions – depicted by closely spaced hachured lines; the “tics” on the contour lines point • toward the center of the depression. • Rule of V’s – contours “V” upstream (depicts equal elevation across a stream valley). • Index Contours/Index Lines – every 4th or 5th contour line is darker than the others and has the elevation labeled. To Determine the Contour Interval (CI) on a Topographic Map: 1. Find the labeled elevation of 2 consecutive index lines; subtract the lower elevation from the higher elevation to find the vertical distance between the two index lines. 2. Count the spaces between the 2 index lines 3. Divide the vertical distance you obtained in step 1 by the number of spaces. Elevation – altitude; the height above a datum surface (sea level). NGVD – National Geodetic Vertical Datum: formerly called "Sea Level Datum of 1929" or "mean sea level". The datum was found by averaging the sea level over a period of many years at 26 tide stations along the US and Canada coastlines. Relief – vertical distance between high and low points in a given region. Benchmark – a precisely determined elevation above or below a standard datum (sea level).
Graphic Scale – a line or bar drawn on the map and divided into units that represent ground distance. This is good for photo reduction/enlargements of maps.
Contours:
http://erg.usgs.gov/isb/pubs/booklets/symbols/reading.html http://mac.usgs.gov/mac/isb/pubs/factsheets/fs01502.html How topographic maps are made: http://erg.usgs.gov/isb/pubs/booklets/topo/topo.html
MAP BOOK EXERCISEFOR LAB #7 NAME ______________________________________________ Turn to page 17 of “100 Topographic Maps” books and answer the following questions: 1.
Look at the contour lines adjacent to the intermittent stream (C-E/4) and determine which end has the higher elevation, C or E.
2.
What is the main difference in the structures at E/5 (BM 5043) and D-E/1 (BM 4638)?
3.
Name the structure from B-D near the far left margin of the map (left of 1).
4.
What structure is represented from the top of Cedar Mountain (B/3-4) to Antelope Sink (C/4) where the contour lines zigzag?
5.
Why are the contour lines on Cedar Mountain ‘squiggly’ rather than smooth?
6.
What term is used to describe darker lines with contour intervals marked on them?
7.
Without looking at the legend, explain how to determine the contour interval of this map.
8.
What is the relief from Antelope Sink to the Bench Mark at the top of Cedar Mountain?
INTRO EARTH SCIENCE LAB EXERCISE FOR LAB #7 Name_______________________________________ PROFILE OF A VOLCANO
A Label the profile elevations from sea level (0) to 800 feet.
A’
EXERCISE FOR LAB #7 NUMBERING CONTOUR LINES Name__________________________________ Refer to the map below and answer the following questions: 1.
What is the contour interval used on this map? ___________________________
2.
Write the correct contour number directly on each contour line.
3.
Write the value of each Benchmark indicated by an ‘x’. (A) __________________ (B) __________________ (C) ________________ (D) __________________ (E) __________________ (F) ________________
4.
What is the name of the darker contour lines? _________________________
EXERCISE FOR LAB #7 PROFILE OF LAB #7 MAP 1. Use a ruler to draw a PROFILE LINE on the preceding map from the SW corner to the NE corner, making sure that you transect areas of benchmarks FX and CS. Label the SW end of the line: A Label the NE end of the line A’ . 2. On the profile lines below, using a CI of 25 feet, label elevations from 1000 to 1200 along the left border. 3. Below, draw the PROFILE from A to A’. Label benchmark FX and CX on you profile.
A
A’
Notes for Lab #8: Structural Geology
Earth Lab Chapter 7
Structural Geology – the study of the deformation of subsurface rocks. Geologic Map – map showing the distribution of various rock bodies, formations, structures, and age relationships. Planar Features – defined by strike, dip, and dip direction • Strike – the trend of a horizontal line in the plane measured with respect to North. • Dip – the vertical angle of a plane measured with respect to the horizontal. • Dip Direction – perpendicular to the strike.
Clinometer Mode – turn the compass dial setting 90 degrees at the hinge. Folds – bending without displacement. • Anticline- oldest beds are in the core of the fold, as above • Syncline – youngest beds are in the core of the fold. Fold Axis – line about which folding takes place. Compression – forces or stresses perpendicular to the fold axis. Limbs – sides of the folds; the area of a fold between adjacent fold hinges. Horizontal Fold – fold axis is horizontal. Plunging Fold – a fold with an axis that is NOT horizontal. Fracture – a break along an irregular surface. Joint – a fracture WITHOUT displacement. Fault – a fracture WITH displacement.
GEOLOGICAL MAP EXERCISES FOR LAB #8: Using Map #1 of the Grand Canyon Bright Angel Quadrangle write the answers for the following questions. 1.
Locate the BRIGHT ANGEL FAULT.
2.
Name one of the 3 MONOCLINES.
3.
Locate a (very small) THRUST FAULT.
4.
Write the location and elevation of any BENCHMARK.
5.
Using the STRIKE & DIP symbols on this map, write the general DIP DIRECTION of the area.
6.
Name a MISSISSIPPIAN-aged formation.
7.
Name and locate the OLDEST formation.
Use Map #4 of Pennsylvania to answer the following questions. 1.
Name the GEOLOGICAL STRUCTURE located at the bottom and center of this map.
2.
What is the EVIDENCE for your answer.
3.
What is the direction of PLUNGE?
Use Map #5 of Devil’s Fence Quadrangle to answer the following questions. 1.
Name the GEOLOGICAL STRUCTURE in the eastern half of this map.
2.
What is the direction of PLUNGE?
Notes for Lab #9: GEOLOGIC TIME
Earth Lab Chapter 8
Stratigraphy – the study of strata (sedimentary and volcanic layers). Relative Age – the geologic age of a fossil, rock, geologic feature, formation, or event defined relative to other fossils, rocks, features, formations, or events, rather than in terms of years, i.e. “this trilobite fossil is older than that dinosaur skull”. Absolute Age – the numerical, geologic age of a rock or formation given in units of time. This is determined by the radioactive decay of elements (radiometric age), and involves a margin of error. Radiometric Age – an age expressed in years and calculated from quantitative determination of radioactive elements and their decay products (a short half-life element is C-14 and long half-life elements are K-40/Ar-40). Paleontology – The study of the forms of life existing in prehistoric or geologic times, as represented by the fossils of plants, animals, and other organisms. Fossil – evidence of pre-existing life. Trace Fossil – marks or tracks left by plant or animals, e.g. foot prints, tooth marks, burrows, etc. Index Fossil – Fossils of organisms that existed for a short period of time. They are a useful tool in correlating the age of rocks and other species present in the same strata. Principle of Faunal Succession – the observed chronologic sequence of life forms through geologic time. Organisms evolve in a definite order. Species evolve, become extinct, never to reevolve. Principle of Original Horizontality – sedimentary strata are horizontal when deposited; strata that are not horizontal have been deformed by movements of the crust. Principle of Stratigraphic Superposition – in any section of undisturbed sedimentary strata, the oldest stratum is at the base and the youngest is at the top. The order of deposition is from the bottom upward. Principle of Cross Cutting Relationships – a rock body or feature that cuts across another rock body or feature is the younger of the two. Conformable Sequence – a sequence of sediments laid down consecutively without any interruption (hiatus) in the rock record. Hiatus – a lapse in geologic time. A gap or interruption in the sedimentary sequence; this may reflect a period of erosion or a period of non-deposition. Unconformity – a gap in the rock record due to uplift and erosion or from non-deposition.
Continued→
NOTES FOR LAB #9 (page 2) TYPES OF UNCONFORMITIES: Nonconformity – submergence and deposition of flat-lying beds over crystalline rocks.
Erosional Surface →
Disconformity – submergence and deposition of flat lying beds over flat-lying beds.
←2nd depositional events Erosional Surface → ← Earlier depositional events
Angular Unconformity – submergence and deposition of flat-lying beds over tilted or dipping
←2nd depositional events
Erosional Surface →
← Earlier beds deposited; then tilted by tectonic event
Geologic History (Ordering of Geologic Events) – sequence of geologic events in the order of occurrence. EXAMPLES (1 being the earliest):
1
Horizontal beds deposited in basin
2 Beds tilted, uplifted, & eroded; submerged : second depositional events
3 Faulting: Normal fault
4 Igneous intrusion
EXERCISE FOR LAB #9 : Name
ORDERING OF GEOLOGIC EVENTS
For each of the following cross-sections, correctly identify the proper order of geologic events, oldest to youngest. A.
B.
C.
EXERCISE FOR LAB #9 : Name D.
E.
F.
ORDERING OF GEOLOGIC EVENTS Continued
EXERCISE FOR LAB #9 : Name G.
H.
ORDERING OF GEOLOGIC EVENTS Continued
Notes for Lab #10: SHORELINES AND OCEANS
Earth Lab Chapter 12
Continental Margins - The shorelines, shelves, and slopes of the continents. Margins on the East Coast of the United States are Passive Margins; they are far from a plate boundary so volcanoes and trenches are absent and earthquakes are few. Continental Shelf - A gently sloping area of shallow water adjacent to a continent. Where the continental and oceanic crusts meet, the continental shelf slopes steeply seaward and is called the Continental Slope. Peninsular Florida rests on The Florida Plateau (Fig 10.1), a broad flat carbonate platform that extends offshore to a depth of 300 feet. Florida's continental slope begins at the edge of the Florida Plateau (Florida's continental shelf). On the west coast the edge of the plateau extends far out into the Gulf of Mexico (200 km). But on the east coast, south of Cape Canaveral, the shelf is narrow and steep permitting higher wave energy to impact the east coast.
The relatively broad shelf off the northeast Florida coast and the Bahamas Bank off the remainder of the east coast offer shoreline protection from Atlantic waves. The Bahamas Bank is separated from the mainland by the Straits of Florida (depth to 760 meters). On the east coast the mean significant wave height during winter months is about 1.2 meters.
When the sea level was lower (during ice ages), Florida's landmass extended into what is now the Gulf of Mexico; however, during sea level rises Florida has disappeared entirely.
Surficial quartz sands mantling south Florida are called Pamlico sands. These were at the bottom of the sea when the sea level was 25 feet higher than present and all of South Florida was submerged (Figure 10.2). The Pamlico sands are a paleo-marine terrace. When sea level lowered during the Wisconsin Ice Age, the Pamlico sand was left behind to be shaped by the wind into dunes and beach ridges. Broward County has abundant surface deposits of siliceous (quartz rich) Pamlico sands.
Florida's present coastline extends for 1,350 miles. The modern coastal morphology is the result of about 15,000 years of rising sea level following the last ice age. During the past 3,000 years the rate of rise has slowed to about 4 cm per 100 years. At times in the geologic past the sea is estimated to have risen at the rate of 1 cm per year (1 meter per century).
Longshore Drift – Rivers and streams from the Piedmont region of Alabama, Georgia, the Carolinas, and Virginia supply the longshore current with quartz sands which reach Florida as longshore drift. Longshore sediment transport falls off significantly by the time the longshore current reaches Miami. The rate of transported sediment along the entire east coast north of Cape Canaveral is 500,000 cubic meters/yr. The sediment transport rate for Miami’s shoreline is only 10,000 cubic meters/year.
Cape Florida, the extreme southern tip of Key Biscayne, is now the principal southern terminus of the siliceous sands that wash down the East Coast on the longshore current.
Beach sands south of Cape Florida are carbonate sands, mostly of biogenic origin.
Overall, longshore transport is from north to south along the peninsula beaches and from east to west along the panhandle coastline (due to a combination of frontal conditions).
Florida's 5 Coastal Zones (See Figure 10.3): 1. The east-coast barrier island system (discussed below) 2. The mangrove coast of southwest Florida, between Cape Sable and Cape Romano, has mangrove swamps, abundant oyster and worm reefs and is tide dominated due to the broad continental shelf. This includes the Ten Thousand Islands. 3. The Gulf barrier-island system: Extends from Anclote Key on the north to Cape Romano; this includes Siesta Key, Sanibel Island and Marco Island. 4. The marsh coast of the Big Bend area - Extends from the Apalachicola River Delta to Anclote Key—a low energy shoreline due to the extreme width of the Florida Plateau. 5. The panhandle, including the Apalachicola. Delta - wave dominated barrier islands and spits and mainland beaches. Beaches are reputed to be the best in the State. East Coast Barrier Island System - The present east coast of Florida is characterized by quartz-sand barrier islands with 22 inlets. South of Cape Canaveral the islands are wave dominated; north of Cape Canaveral there is a greater tidal influence.
Miami Beach, Virginia Key and Key Biscayne have a foundation of hard coral reef limestone topped by an accumulation of sedimentary sand deposits that began as sandbars. Large portions of these islands were mangrove swamps, especially the western shores. New earth, much of it dredged from Biscayne Bay, was dumped on cleared mangrove swamps to make high ground (real estate). Watson Island, Star Island, Palm Island, etc. are manmade islands made from dredgings. Key Biscayne is unique in that it is a sandbar that partially formed on a petrified mangrove and worm reef. Coquina of the Anastasia Formation provides the rocky anchor for many sandy barrier islands to the north.
Fig.10.1 The Florida Platform and Florida Escarpment Randazzo
Fig. 10.2 Shoreline of the Pamlico Sea when sea level was 25 feet higher than present. Hoffmeister
Fig. 10.3 Florida’s 5 coastal zones
Randasso
THE PATH OF THE GULF STREAM The Gulf Stream currents are born from the constantly blowing easterly trade winds in the tropics and the westerly winds in the northern latitudes. The Coriolis effect from the earth's rotation, along with the wind patterns, causes the water mass to slowly rotate in a clockwise pattern. The trade winds drive the North Equatorial Current from the west coast of Africa, across the Atlantic, through the Antilles and into the Caribbean Sea. This mass of water then passes through the Yucatan Channel between Mexico and Cuba. Some of this water forms the loop current in the Gulf of Mexico, and the rest passes into the Florida Straits where it is squeezed between the Florida Keys and Cuba. The Straits between Key West and Havana are 140 km wide and 1500 meters deep. They become narrower and shallower downstream and reach a minimum cross section off Miami. Here the Florida Current, as the Gulf Stream is called while within the Florida Straits, transports 25 million cubic meters of sea water per second and is bounded by the Florida peninsula and the Bahamas Bank. As it emerges from the Florida Straits north of Bahamas, the Gulf Stream flows across the Blake Plateau along the coasts of Georgia and the Carolinas. By Cape Hatteras it is moving over 60 million cubic meters of water per second. As it veers to the northeast it moves over depths of 5000 m and it develops meanders, which eventually form detached eddies. The northern edge of the Stream brushes across the tail of Grand Banks off Nova Scotia where it mixes with the cold south flowing Labrador Current. This mix produces one of the greatest fisheries in the North Atlantic. As the Stream moves east towards Europe, it breaks up into several broad currents and is called the North Atlantic Current. This splits into a southerly flowing Canary Current past Portugal and northwest Africa and then heads west again as the North Equatorial Current to complete the giant anticyclonic gyre. Within the gyre of the Gulf Stream is the Sargasso Sea, a relatively barren and desert-like expanse of water between the Bahamas and Bermuda. One phenomenon that brings nutrients and plankton into the Sargasso Sea is Gulf Stream cold-core rings. As the Gulf Stream moves east along the northern boundary of the Sargasso Sea, it meanders and forms eddies which entrap cool, nutrient-rich coastal water. These eddies eventually head south into the Sargasso Sea. Satellite tracking has shown that they can remain intact for months or even years.
Bahamas Bank: http://daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/GEO_6/GEO_PLATE_C-16.HTML http://www.oceanweather.com/data/ Gulf Stream Current: http://www.at-sea.org/missions/fathoming/features.html
Notes for Lab #11: GROUNDWATER AND KARST
Earth Lab Chapter 13
Hydrology - The science of the study of the movements and characteristics of water on and under the earth's surface. Hydrogeology - The study of the subsurface waters and related geologic aspects of surface waters. Potable Water - water fit for human consumption. Precipitation is the source of all freshwater in Florida. Runoff - the part of precipitation flowing to surface streams. The St. John’s River is a source of potable water to the Jacksonville area. Groundwater – all subsurface water from rain, snow and streams that infiltrates from the surface to the zone of saturation (below the water table). In South Florida, groundwater is the source of our potable water. Zone of Aeration (Vadose Zone) – subsurface zone immediately below land surface in which pores between grains are filled with air. Water percolates through this zone down to the water table. Zone of Saturation (Phreatic Zone) – subsurface zone in which all pores and fractures and large cavities are filled with water. Water Table – the surface between the zone of aeration zone and the zone of saturation.
Pores – interstices (spaces) in rock and sediment. Porosity – the percent of the bulk volume of rock or sediment made up of pore spaces and/or fractures whether isolated or interconnected. Permeability – the capacity of a porous rock for transmitting a fluid due to the connectivity of pores/fractures. Percolation - downward gravity movement of water through the pore spaces of soils, underlying unconsolidated materials and rocks. Hydraulic Head – elevation of the water table above a datum (at a point in space and time). The relative difference in head between one point and another exerts the fundamental control on the
movement of water, i.e., flow direction and velocity. Water towers artificially provide pressure to a water delivery system by providing an extreme difference in elevation (head). The Rate at which water travels through rock or sediment depends on (1) porosity, (2) size of pores and (3) water pressure (head). Aquifer – a permeable body of rock below the water table. An aquifer contains sufficient saturated permeable material to yield economical quantities of water to wells and springs. •
In southeastern Florida our principal aquifer and sole source of potable water is the Biscayne Aquifer. This is one of the most permeable aquifers in the world. It is wedge shaped, being thickest along the coast and thins westward toward the Everglades. Its high permeability is due to the large connected pores of limestones, sandy limestones, and shelly sand units. Coral rock, oolitic limestone, and coquina, are examples of some of its highly porous rocks.
Unconfined Aquifer - An aquifer where the water table is exposed to the atmosphere through openings in the overlying materials (zone of aeration). •
The Biscayne Aquifer is an unconfined aquifer, which means that pollutants from the surface can enter the aquifer as directly as rainwater (No formation impedes percolation). The fact that the Biscayne Aquifer is unconfined, close to the surface and highly permeable means that contaminants may enter and disperse readily in the Biscayne Aquifer. In Miami-Dade the aquifer is encountered between about 2 and 20 feet below ground surface; on average it is about 9-13 feet down to water. In the western part of the County after heavy rains the groundwater may rise above the land surface. Fluctuations of the Biscayne Aquifer over the course of a year may range from 2 to 8 feet depending on rainfall, location, and pumpage.
Recharge - The addition of water to the zone of saturation. •
Rainfall recharges the Biscayne Aquifer. Along the coast water from flood control canals is a source of recharge. Some of the recharge from canals is contaminated with industrial chemicals, hydrocarbons, and agricultural chemicals.
Aquiclude – a virtually impermeable body of rock, such as shale, through which no water moves. • •
In South Florida there is an aquiclude beneath the Biscayne Aquifer. Clay is the major confining material of this aquiclude. Beneath the aquiclude there is a second (deeper) aquifer called the Floridan Aquifer. The Floridan Aquifer underlies the entire state extending into Alabama, Georgia, and South Carolina. In parts of our State it is the principal source of potable water. In South Florida the water quality of the Biscayne Aquifer is superior to that of the Floridian Aquifer which is highly mineralized. In South Florida wells penetrating into the Floridan Aquifer may be suitable for crop irrigation or industrial applications.
Injection Well - a well designed for the purpose of injecting a fluid down into the cracks, cavities or pores in a rock formation below the earth's surface. • In South Florida injection wells are used to inject industrial wastes and municipal wastes (treated sewage effluent). Wells which inject hazardous wastes into or above drinking water aquifers have been banned in Florida.
Saltwater Intrusion – Sea water readily intrudes into the aquifer when the freshwater level approaches that of the adjacent sea. If freshwater levels are maintained sufficiently higher than sea level the inland movement of seawater is curtailed or reversed. The deeper the aquifer the greater the freshwater head (i.e., the difference between fresh and sea water levels) must be to prevent inland saltwater movement. A one foot head of fresh water will depress 40 feet of salt water in the ground. • In Dade County the two major sources of saltwater intrusion are wellfield pumpage and the canals which sea water invades on the incoming tides. • To hold the saltwater in the Biscayne Aquifer to a position near shoreline, a freshwater head of 2.5 feet is required. This assumes that the aquifer is 100 feet deep. • In south Dade the saltwater barrier line intersects approximately with Red Road in the vicinity of Coral Gables. Water east of the saltwater barrier line is non-potable. Karst Topography – develops from the dissolution of limestone by the weak acid carried in ground water; characterized by caves and sinkholes. Caves – an underground cavity. Caverns – a cave system; several caves joined together. Sinkhole – a cavity open to the sky due to the collapse of a cave roof. Solution Valley – a closed depression formed by the coalescence of several sinkholes; has irregular floor and scalloped margin. Monadnock – an erosional remnant; a landform more resistant to erosion. South Florida’s Surficial Geology
The Miami Limestone has an oolitic limestone facies and a bryozoan limestone facies (Fig 11.1). Oolitic limestone characterizes the Atlantic Coastal Ridge (high ground paralleling the coast. See Fig. 11.2) and lies at or near the surface almost everywhere from Miami southward to the point where the Atlantic Coastal Ridge dies out on the mainland southwest of Florida City. Oolitic limestone reappears once again in the lower Florida Keys, from Big Pine Key to Key West, where Miami oolite is again the bedrock. The lower oolitic keys lie perpendicular to the upper keys. The bryozoan facies of the Miami Limestone is most commonly encountered west of the Coastal Ridge. It has been quarried from FIU's south campus lakes and is a dominant substrate in the Everglades. Bryozoan means "moss animal". A bryozoan is a minute, marine invertebrate that secretes a small, calcareous cell and grows together to form colonies, many of which become a foot or more in diameter and develop knobby structures with hollow centers. They prefer quiet backwater, low energy environments (coral require a high energy, oxygen rich environment). In Florida Bay bryozoan encrusted seaweed may be found.
The Key Largo Limestone is the formation forming the upper Florida Keys. It is corraline limestone, locally called “keystone”. The upper keys are elongate parallel to the shelf edge. The Lower Keys (oolitic) are elongate perpendicular to the shelf edge (Fig 10.1).
Figure 11.1 Geologic map showing areas covered by the oolitic and bryozoan facies of the Miami Limestone Hoffmeister
Fig. 11.2 Generalized Physiographic Map of South Florida. Hoffmeister
Karst: http://daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/GEO_7/GEO_CHAPTER_7.H TML
NOTES FOR LAB #13: EARTHQUAKES
Earth Lab Chapter 10
Earthquake – a sudden motion or trembling in the Earth caused by the abrupt release of slowly accumulated strain. Seismology – the study of earthquakes generated by seismic waves. Seismograph – an instrument that detects and records shocks and vibrations of the Earth, especially earthquakes. Seismogram – a record of the Earth’s motion inscribed by a seismograph. Focus – the initial rupture point of an earthquake; the point within the Earth which is the center of an earthquake. Epicenter – the point on the Earth’s surface that is directly above the focus of an earthquake. Seismic Waves – a general term for all elastic waves produced by earthquakes; they move out from the focus in a 3-d spherical pattern. Surface Waves – seismic waves that travel along the surface of the Earth. Body Waves – seismic waves that travel through the interior of the Earth; P & S waves. P-Waves – primary or push-pull; involves particle motion (alternating compression and expansion) with vibrations parallel to direction of travel; the fastest seismic wave; first to arrive. S-Waves – secondary or shear waves; a transverse wave that involves oscillation perpendicular to direction of travel; does not travel through liquids, such as the outer core. Time Lag – the difference in arrival times between P & S waves. Richter Magnitude Scale – numerical scale of earthquake magnitude (logarithmic; 10 fold increases in amount of energy released). It is an open-ended scale. Modified Mercalli Intensity Scale – a measure of the amount of damage on a scale from I to XII; used by insurance companies to determine damage. Aftershocks – less severe earthquakes that follow the main shock and decreases in frequency and magnitude with time (days and months) Earthquake Damage – due to ground movements, landslides, liquefaction and tsunamis. Landslides – processes of down slope transport of soil and rock material en masse due to gravity. Liquefaction – the transformation of loosely packed sediment from a solid into a fluid mass that slides down slope following an earthquake. Tsunami – huge waves generated by abrupt physical displacement of the ocean floor due to earthquake or volcanic activity. Nearly all originate in the Pacific Ocean. Triangulation – to determine the location of the epicenter of an earthquake. Measure time lag between P & S waves, calculate distance to the epicenter from each seismic station using velocity of P & S waves, then draw circles from at least 3 seismic stations, and the epicenter will be at the intersection of the circles.
