Earth Science Module 22 Earth History: The Rocks Cry Out Main points of module on earth history:  Various data tell which rocks are older and which are younger, but putting year ages on rocks requires assumptions about radioactive decay that cannot be verified.  Organisms that once existed have left fossils, and fossils combined with the rock are compiled into a composite diagram called the Geologic Column that summarizes the history of the Earth.  Conventional models place dates on the Geologic Column and the history of the earth suggesting 4.6 billion years of geologic and biologic evolution.  Creation models relate the Geologic Column to a recent creation, the bulk of fossil-bearing rock to a one-year catastrophic global flood, and the rest to few thousand year recovery from that global catastrophe. Earth History Module Study Notes and Outline Rock Clocks or How to Put a Date on a Rock I. Telling time for earth history A. A geologist wants to know the history of the rocks of the earth and a paleontologist want to know the history of life on earth. 1. History requires a time context to know when something happened. B. Scientists were not there to see the event. 1. Creation scientists consider the Bible to provide an eyewitness account though given in very sketchy terms. 2. Conventional scientists do not consider the Bible to be an appropriate eyewitness account. 3. Therefore conventional scientists seek indirect and circumstantial evidence to put dates on events. 4. Even creation scientists have to associate particular geological and fossil data with dates in the Bible, and that takes interpretation, too.

C. When conventional scientists look at rock and fossils, which look very old, and see geologic processes happening very slowly today, they conclude that it has taken a very long time to build the rock layers. D. As a result scientist have devised two ways to estimate the dates in earth history— relative dating and radiometric dating. II. Relative Dating—this is simply determining that Rock A is older or younger than Rock B. No actual time is stated. Relative ages are determined by the principle of superposition A. Principle of superposition—this states that younger rocks lie above older rocks. 1. The idea is simple—like the layers of a cake. The law of gravity prevents a top layer to be put into place before a lower layer is in place. 2. Generally the layer sequence indicates that each layer was laid down without interruption between deposition of the layers. B. Unconformities—However, there is evidence of interruption between deposition of layers. 1. This interruption makes a contact surface between layers called an unconformity. 2. Unconformities can be formed by a lower layer that was eroded away or by sediment that failed to be deposited before the next layer was deposited. C. Exception to superposition 1. We have already talked about intrusive igneous rock in Module 4. Molten rock can move up through crack or faults in older rock. 2. In mountain building, forces are so great that along a fault, older rocks can actually be pushed up over the top of younger rocks. D. Relative dating is used by both conventional and creation scientists. It is just putting an order to the sequence of rocks. III. Radiometric Dating (Conventional science uses this for “Absolute Dating” but creation science uses it with caution only for relative dating). It is based on the property of certain unstable atoms to break down into other atoms in the process called radioactive decay. A. Radioactive Decay 1. An element can have different forms called isotopes. 2. Radioactive decay is the process in which the atoms of an unstable isotope convert into a different isotope (of that or a different element) and nuclear energy is given off. The original isotope is called the parent and the new isotope after decay is called the daughter. 3. What is important about radioactive decay is that no matter the original number of parent atoms, half of these become daughter in a certain time that is consistent for each parent isotope. This amount of time is called the half-life. a. In the second half-life, half of the remaining parent atoms are converted to daughter. So there is one fourth of the original parent element left.

b. In the third half-life, half of the remaining parent atoms convert to daughter, so there is one eighth of the parent left. c. And so on… For every half-life, half of the parent element is lost. B. Dating assumptions--So, if you know how much parent was there to begin, you just have to count the number of daughter atoms, calculate the number of half-lives, and then you know the age of the rock—in theory. To get this date, though, you have to make three assumptions. 1. When the rock first formed there was no daughter isotope. 2. There was no influx or leakage of parent or daughter during decay. 3. The rate of radioactive decay has not changed—the clock has ticked the same. C. We can test for the first two assumptions using special methods. We can figure out how much daughter isotope is contamination and how much chemical (not nuclear) change has taken place over the years. This method is called the isochron method. D. Dating problems—Even with isochron dating, there are important examples of radiometric dating producing strange results. For example, some modern lava flows that we know from historical records are not even 2000 years old give radiometric ages millions or even billions of years old. Other ancient rocks have been dated using different parent/daughter isotope combinations, and they yield very different results. So radiometric dating isn’t always reliable. E. There is still a trend. Even though the dates of some samples are clearly not right, overall, there is still a trend in the rock record. For example, in rock layers where we can be sure about the relative dating, the radiometric dates usually support the relative dates. In other words if layer A sits on top of layer B, radiometric dating usually shows that layer B is older than layer A. 1. Thus, conventional scientists are confident that radiometric dating is usually OK to use. Even though there are problems, in most cases radiometric ages are considered to be reasonable. 2. Creation scientists skeptical of radiometric dating need to provide an explanation for the general pattern, even though we know that radiometric dating methods don’t always work out. F. Types and “ages” 1. U-Pb (Uranium to Lead) Half-life is 4.5 billion years –used for very old rocks and meteorites. 2. Rb-Sr (Rubidium-Strontium) Half-life is 49 billion years—old rocks and meteorites 3. K-Ar (Potassium-Argon) Half-life is 1.3 billion years—medium aged rocks 4. C-14 (Carbon 14) Half-life is only 5,700 years—for organic remains (bones, hair, mummies, etc.) less than 50,000 years. Unlike the other methods, C-14 cannot be used on rocks or fossils. G. Dating sedimentary rocks

1. Since sedimentary rocks are formed when sediments are laid down and cemented, the radioactive minerals in them will give date when the mineral was made, i.e., much older than when the sediments were deposited. 2. Therefore sedimentary rocks cannot be dated directly by radiometric methods. They are dated by adjacent igneous or metamorphic rock. So, if the sedimentary rock was deposited after igneous, the sedimentary rock will be younger than the igneous. If it below igneous rock, it will be older than the igneous. Scientists hope to find sedimentary rock sandwiched between igneous rock to get an upper and lower date to limit the age of the sedimentary rock. H. Creationist interpretation of dates 1. First, creationist scientists generally reject the radiometric dates that conflict with our understanding of earth history from the Bible. 2. As we explained above, there is still a pattern to radiometric dates. Consequently, creationists think that you could use radiometric dates to give relative dates of two rocks. One might be older than another, even if the actual difference in time could be just a matter of days, not of millions of years. a. That is, the relative radiometric dates still have to be placed within a youngage sequence of only several thousand years. b. There is even the possibility that when a creationist nuclear physicist (that might be you) learns enough about the physics of radiometric decay, we can actually use radiometric decay to calculate the age of the rock in a young-age framework to the year, month, day, and hour the rock was formed at or since creation.

Earth History Module Study Notes and Outline Fossils and the Geologic Column IV. Fossils—have you ever picked up a rock and seen something that looks like a leaf or a bone preserved in the rock? That is a fossil. A. What is a Fossil—it is the physical evidence of an organism preserved by geologic processes. 1. It usually consists of the remains of an organisms but there are other types, too. B. Different types of Fossils 1. Original preservation—the organism or its parts are still there due to: a. entrapment in amber, or tar, or rock b. freezing in arctic or alpine areas c. drying out in deserts (mummified) d. “pickled” by plant acids – “pickled” means chemically altered so it doesn’t rot away 2. Altered hard parts—skeleton or woody parts become surrounded by precipitated minerals or are replaced by minerals. This is called petrifaction. 3. Impressions—the rock surrounding the body hardens, often after squishing the organism nearly flat. The organism decays or leaves a layer of coal-like carbon and rock material fills in where the organism was. a. The hardened rock around the cavity is called the mold. b. The shape made by the rock material filling in the cavity is called the cast. c. The mold and cast are mirror images of each other. 4. Trace fossils—these are evidences of an organism having been in the location and include things like footprint impressions, burrows, and preserved dung. C. How are fossils formed?--Rapidly 1. In order for fossils to be formed, the organisms must not decay or be eaten before burial or entrapment. Therefore burial must be rapid. 2. For rock fossils, this means the organisms must be caught up while alive or recently killed and mixed with the sediment or deposited between two pulses of sediment deposition. 3. The sediment surrounding the body squeezes the air out and prevents bacteria or fungi from rapidly decomposing the body. 4. If bones are all tumbled together, then the animal partly decayed so that the skin and ligaments rotted to the point of not holding the bones together before they were buried.

V. Geologic Column A. The rock record 1. In the last lesson we talked about the principle of superposition to determine the relative ages of different layers of rock. 2. However, due to unconformities, not all the layers of rock are present at all places on the earth. a. Most places have just a small subset of all the possible rock layers from around the world. b. In fact a particular locality may have a few layers from early rocks, a few layers from medium old rocks, and a few layers of recent rocks. c. So how do we know what the full sequence is? B. Principle of Correlation 1. Different layers of rock have different characteristics of mineral composition, color, texture, and fossils. Thus the particular combination of several different layers and their characteristics give the sequence at any one place a “fingerprint.” 2. The geologists looks for overlapping sequences with the same fingerprint to build up a larger sequence. This lining up of overlapping unique sequences is called the principle of correlation. 3. So where some layers are missing in one area due to an unconformity, the information is filled in by sequences from adjacent localities. 4. The ideal sequence for the whole world, built up by correlation of smaller sequences is called the geologic column. C. Rock types vs. time 1. Geologists in the 1800s grouped the rocks in the geologic column into four major groups based on similarities in the characteristics of the layers. These are: a. Primary – for the lowest set of rocks b. Secondary—for the middle set of rocks c. Tertiary—for the rocks near the top d. Quaternary—for the thin layer of distinct rocks at the very top of the column 2. Each of these was subdivided into small sets called Systems, and each System was further divided into yet smaller groups of layers called Series. 3. Later, rocks were discovered that were below the Primary rocks in the geologic column. Since the lowest System was called the Cambrian, the lower rocks were called the Precambrian rocks. 4. As I said in the last lesson, geologists want to provide a time context for earth history, so they used the geologic column as a calendar to summarize time differences and assign radiometric ages to each. When the geologic column is used as a time scales it is called the geologic time scale. Therefore in the

geologic time scales the major groups (e.g., Primary) become Eras, the Systems become Periods, and the Series become Epochs). D. Diagram of Geologic Column. Here is a diagram of the Geologic column. When you add radiometric ages it becomes a Geologic time scale.

“2 my”

“65 my”

“250 my”

“500 my”

“4000 my”

1. Thus, with the evolutionary emphasis of the geologic time scale, the Primary rocks become the Paleozoic (old life), the Secondary becomes Mesozoic (middle life), and the Tertiary and Quaternary become the Cenozoic (young life) E. Creation scientists (who are professionally trained) only accept the geologic column, not the geologic time scale. 1. They use the terms Systems and Series, but generally it is just too hard to communicate with conventional scientists without using the terms for the eras. So when creation scientists used these terms, they are only using the information from the characteristics of the rocks summarized in the geologic column, not the radiometric ages. VI. Ways To Relate Fossils And The Geologic Column A. How to explain the Fossil Sequence—it is interesting that as one moves up the geologic column, the fossils change, often from very simple organisms to more and more complex organisms. How is this increasingly complex fossil sequence interpreted?

1. Conventional Science—Since conventional science sees millions to billions of years in the geologic column, the fossil sequence is seen as creatures evolving and entering the fossil record while others become extinct and disappear. 2. Creation science—Since creation science sees only several thousand years in the geologic column, the fossil sequence is seen as the sequence of destruction during Noah’s Flood and in the localized catastrophes after the Flood.

Earth History Module Study Notes and Outline Precambrian and Paleozoic Rocks VII.

Comparison of Interpretive Frameworks

A. In these last two lessons on earth history, we will compare conventional and creationist interpretations of the rock record, fossil record, major events and timing. B. For this lesson, we will focus just on the Precambrian and Paleozoic rocks. VIII. Conventional Old-Age Interpretation of the Precambrian Earth and the Paleozoic Era A. Conventional geology has broken the Precambrian into three major rock units associated with 4 billion years of time called Eons. 1. These are: a. Hadean – 4.6 to 4 Bya (Hades) – Hadean is known only from a few small rocks from Australia, Greenland, and Canada. This is when the earth first cooled and the first igneous rocks were formed. b. Archean – 4 to 2.5 Bya (Ancient) – This is when land and mini-continents formed and primitive life forms first arose. In the Late Archean, reef-forming photosynthetic bacteria evolved and increased. c. Proterozoic – 2.5 to 0.5 Bya. (Forerunner life) - There are lots of both Archaean and Proterozoic rocks known. i. This is when Rodinia formed, the atmosphere became oxygenated, and first single celled animals and plants evolved. ii. During the Late Proterozoic, Rodinia began to split apart. The first multicellular animals evolved in shallow seas around Rodinia and in the new developing sea ways. They had thin, soft-bodies, do not appear to be related to later animals, and went extinct before the Paleozoic. 2. The Paleozoic (beginning at 0.5 Bya or 540 Mya) The Paleozoic (beginning at 0.5 Bya or 540 Mya) is broken down into periods, which are given next. B. The Cambrian Period (about 540 to 490 Mya), the beginning of the Paleozoic Era. 1. In the coastal waters surrounding the remnant continents of Rodinia, every major group of animals and algae with living representatives evolved in a short time. This is called the Cambrian explosion. Since the soft-bodied animals of the Proterozoic appear unrelated, the origin of the Cambrian animals is mystery. C. The Ordovician and Silurian Periods (490 to 415 Mya) 1. Fish and many seashell groups evolved in the shallow oceans surrounding the drifting continents.

2. Ozone now protected the land so that simple land plants could evolve from aquatic algae along the coastal fringes of the continents. D. The Devonian and Carboniferous Periods (415 to 300 Mya) 1. Continental lowlands were extensive and covered with swamps. This provided a place during the Devonian for several plant groups to evolve from the Silurian plants. 2. In the Carboniferous, large tree-like plants grew in the swamps where peat built up from the dying plants. Because this peat turned to coal when it was later buried in rock, these are called the Coal Swamps or Coal Forests. 3. Winged insects evolved. Fish-amphibian transitional forms and then amphibians evolved in the swamps. E. The Permian Period (300 to 250 Mya) 1. The continents began to reassemble and by the end of the Permian the supercontinent Pangea was complete. 2. The Coal Swamps were replaced by upland forests. 3. Early Reptiles became dominant. IX. Creationist Young-Age Interpretation of the Precambrian and Paleozoic (Primary) rocks. This story of the fossil record is based on the latest creationist research, which is very much a work in progress. It might be correct about some things and wrong about others. Just because we find out later that our creation science interpretations were wrong, we do not abandon our belief in God or the Bible. Interpretations come and go, but God’s Word will never change. A. At the end of Creation Week: 1. All the Precambrian basement rocks were in place. Differentiation into Hadean, Archean, and Proterozic rocks were due to different processes that happened on Creation Day 3, as well as the next 1600 to 2000 years prior to the Flood. 2. All land formed the supercontinent Rodinia and the air was fully oxygenated. 3. All the major groups of organisms were living in specific areas. a. In the open ocean well beyond the reefs, large floating forests occupied continent-sized areas. i. The edges hosted the simplest, most algae-like land plants where the mat was thin. ii. Toward the middle, the mat was thicker with lots of peat and pools of standing water where the Coal Forest plants (the ones with air channels in them), dragonflies, fish-like and true amphibians lived. b. On Day 3 or shortly thereafter, magma intruded the edge of the continental shelves allowing the development of reefs of photosynthetic bacteria with single-celled algae and protozoans abundant in the water nearby

c. In the floors of the shallow seas between the reefs and the shore, the extinct soft-bodied multicellular animals flourished. d. The “Cambrian Explosion” animals occupied the coastal water nearest shore. B. Initiation and Early Stage of Noah’s Flood (about 1650 to 2200 years after Creation) 1. The sea floor began subducting and the mid-ocean floor ripped open with magma eruptions. 2. The first thing that happened was the continental shelves collapsed forming the Proterozoic reef fossils, with the single-celled organisms being buried on top of that, then the soft-bodied animas buried on top of that—all of the Proterozoic sedimentary strata. 3. Next, the offshore sediments and “Cambrian Explosion” animals fell in on top of the Proterozoic strata and were buried in the Cambrian System rocks. 4. The next thing to be destroyed was the floating forest. Because of the huge size of these forests, the destruction began at the outside and progressed inward. These organisms and sediments were washed over the continental margins and lowlands of the now fragments of Rodinia. C. Full Force of the Flood 1. This happened as the continents were ramming into each other again to form Pangea. 2. This set the stage for a shift in rock types and organisms as the Flood waters began to cover and swirl over Pangea to form the Mesozoic Systems.

Earth History Module Study Notes and Outline Mesozoic and Cenozoic Rocks I. Conventional Old-Age Interpretation of the Mesozoic Era A. The Triassic Period (250 to 200 Mya) 1. We pick up when Pangea becomes complete. Because the interior was so far from the ocean it was arid—desert or semidesert. The south extended to near the South Pole and was cold. 2. Dinosaurs evolved in the Early Triassic. Gymnosperms (plants like pine trees) became dominant. B. The Jurassic Period (200 to 145 Mya) 1. Seaways developed as Pangea continued to break apart. This resulted in moister climates throughout. 2. Birds and mammals evolved, and dinosaurs became dominant. The first flowering plants evolved. C. The Cretaceous Period (145 to 65 Mya) 1. The developing oceans enlarged and seaways that are not due to rift valleys covered large parts of continents. The climate became more tropical. 2. New species of dinosaurs replaced the Jurassic dinos (example T. rex replaced Allosaurus—Most dinosaurs of “Jurassic Park” were not Jurassic!) 3. Dinosaurs that walked in coastal mud flats leaving footprint fossils and laying eggs in nests and rearing young. 4. Dinosaurs became extinct at the very end of the Cretaceous, perhaps due to an asteroid impact. II. Conventional Old-Age Interpretation of the Cenozoic Era A. The Paleogene Period (65 to 23 Mya) 1. The Alps and Himalayan Mts. began forming as Africa and India pushed against Europe and Asia. 2. The Mesozoic seaways drained but the climate remained tropical in the Early Paleogene dominated by tropical forests. 3. There was an abrupt change from widespread, thick sediments associated with the seaways to more local, thinner sediments associated with mountain building. 4. In the Late Paleogene, the climate began to cool and dry out as Antarctica developed a permanent ice cap. Grasslands became common. 5. Diverse mammals and bird groups evolved. B. The Neogene Period (23 to approximately 2 Mya)

1. The Cascades, Sierra Nevadas, and Andes formed from subduction along the western margins of the Americas. 2. The climate cooled and dried more with the Arctic ice cap forming. 3. Mammal diversity peaked and then many species went extinct as forests disappeared. The ancestors of humans evolved from apes in the Middle Neogene. 4. The first humans evolved on the grasslands of Africa in the Late Neogene C. The Quaternary Period (Approximately 2 Mya to the present) 1. This is the “Ice Age,” when 4 major glacial advances covered northern North America, northwestern Eurasia, and the mountains in the southern hemisphere. 2. New mammal species evolved that were adapted to the cold climate. 3. Water tied up in glaciers allowed the sea level to drop enough to make land bridges. 4. Modern humans evolved about 150,000 ago and spread from Eurasia to the Americas on a land bridge. 5. The last glaciers melted about 11,000 years ago and modern conditions developed with the extinction of many ice-age species. III. Creationist Young-Age Interpretation of the Mesozoic and Cenozoic Rocks A. Middle to the end of Noah’s Flood (Mesozoic Systems) 1. We pick up when the Flood waters begin to cover and swirl over Pangea. 2. Apparently, there was an area of the pre-Flood world where dinosaurs lived away from most modern creatures. Sediments from this area were deposited as the Mesozoic rocks. 3. The last surviving dinosaurs tried to run from surges of rising water (fossil footprints) and a few pregnant females tried to hurriedly lay eggs just before they were destroyed. 4. These dinosaurs finally drowned and were buried in sediment layers above their footprints and “nests.” 5. No fossils were preserved from the place where humans and modern animals lived, as it apparently was utterly destroyed in the Flood. All mammal and birds fossilized were weird creatures that lived in the dinosaur region.

B. End of the Flood Transition to Dry Land--Lower Paleogene System (Up to a few decades after the Flood) 1. A year after the Flood began, the last of the flood waters retreated washing some dead animals from higher to lower areas. There was still lots of volcanic activity, mountain building as plate tectonics still retained some momentum, and still lots

of intense storms. All of these smaller catastrophes formed Paleogene rocks and fossils. 2. The people and animals left the ark, and plants fragments and seeds settled on the drying mud. 3. At first the climate was very warm because the ocean was so warm from the magma from the Flood so tropical forests regenerated quickly. C. Early Recovery from the Flood—Mid Paleogene to Upper Neogene Systems (a few years or decades to several hundred years after the Flood) 1. Volcanism, lots of mountain building, and persistent storms continued eroding and depositing more sediments as Middle and Upper Paleogene and Neogene System rocks. 2. Animals spread out over the earth, and plants and animals diversified by rapid expression of created, designed, but hidden genetic potential—most of the modern mammal groups descended from their ancestors that were on the Ark. 3. Various ape groups, including those more resembling humans diversified in Africa and some fossilized in Upper Neogene and Lower Quaternary System rocks D. Middle Recovery—the Ice Advance—Lower and Mid Quaternary System (as early as 100 years to as much as 1000 years after the Flood) 1. By the time the continents had cooled enough for snow to fall, the ocean was still warm enough in the subpolar regions for lots of evaporation. 2. Snow fell in excessive amounts but did not melt in summer because the continents were cooled by volcanic dust continuing to block sunlight. 3. Ice sheets formed, repeatedly grew and shrank and then finally melted when the volcanic action let up and the ocean cooled too much to generate warm, moist air in the far north. 4. Humans finally dispersed from Babel and diversified, some divergent forms being fossilized in Africa and Asia in mostly Mid Quaternary rocks. 5. Humans and some animals reached the Americas via land bridges while sea level was lowered by the ice sheets. E. Late Recovery—Upper Quaternary System (as early as 300 years after the Flood to the present, the last 3000 to 4000 years. 1. The climate warmed and deserts began to form. 2. Volcanism, plate tectonics, earthquakes, and storms had slowed to present levels and rates. 3. Mammals suited for the Ice Advance died out after the ice sheets melted, and current species diversified.

4. Humans had reached all habitable continents, and all forms except modern humans were extinct. F. Remember that this creationist understanding of earth history is an ongoing area of research. What we’ve talked about here is not the absolute truth nor the final word. There are many problems yet to be solved and many new discoveries to be made. Perhaps you can continue your studies in science and help creationists reconstruct the true history of the earth.