Dr. Jason Lisle: Creation 101: Geology Part 1 (original source here)
Geology is the study of the physical processes of Earth from plate tectonics and volcanos to minerals and rock layers. The field involves a combination of operational science and origins science. The operational aspects involve measuring the types of rocks and minerals and where they occur, and current observable processes. These things are all testable and repeatable in the present. Geologists often attempt to reconstruct past events on the basis of their observations of present conditions. It is in this area of origins science where creationists and evolutionist will often interpret the same evidence differently.
Geology is one of the most advanced disciplines of creation science. There are at least two reasons for this. First, the Bible gives some very specific details about the Earth’s geological past, including some specifics of the original creation of the planet, and also many details pertaining to the global flood. These historical facts have enabled creation scientists to develop detailed geological models. We are able to explain things like plate tectonics, volcanos, the geologic column, and the ice age in light of the history recorded in Genesis.
A second reason is the publication of The Genesis Flood in 1961. This book was written by the late Dr. Henry Morris and Dr. John Whitcomb. Dr. Morris’s background in science specializing in hydrology made him an ideal researcher on the topic of flood geology. Dr. Whitcomb’s education is in theology; his doctoral dissertation was on the Genesis flood, making him the perfect candidate to write on biblical issues. In the 56 years since its publication, creation scientists have refined the geological models proposed by Morris and Whitcomb. Nonetheless, to this day, The Genesis Flood remains a masterpiece of scientific and biblical research.
When it comes to the operational science aspects of geology, creationists and evolutionists are largely in agreement. After all, the power of operational science lies in its testability. Disagreements can be settled by performing an experiment. And so we all agree on the composition of rocks, where they are found, and how they form today. So it may be helpful to review some of the basics of operational geology.
Rocks and Minerals
Rocks are solid combinations of minerals. A mineral is a naturally occurring, solid, (mostly) inorganic, chemical with an orderly crystalline structure. Table salt is one example. It is sodium chloride (NaCl), meaning it is made of sodium and chlorine ions in equal proportions held together by an ionic bond. It has a crystalline structure that tends to form cubes. Quartz is another example of a mineral. A rock will contain several different minerals mixed together.
Rocks are classified into three primary categories based on how they form today. Igneous rocks are those which formed at high temperature, having solidified from lava or magma as it cooled. Volcanic rocks are igneous. Igneous rocks can form underground as well. Common examples of igneous rocks are basalt and granite. Igneous rocks are those that are used in the process of radiometric dating.
Sedimentary rocks are those that were deposited by water or air. At high speed, water can transport and deposit sediment such as sand. If the sediment contains a cementing agent such as calcite, the grains can lock together, forming a rock. Some examples of sedimentary rocks are sandstone, shale, and limestone. Sedimentary rocks often contain fossils – the mineralized remains of organisms.
Metamorphic rocks are those which were once either sedimentary or igneous, but have been altered by heat and/or pressure. Common examples are marble, slate, schist, and gneiss (pronounced “nice”). Each has an original sedimentary or igneous progenitor. Slate, for example, is produced when shale is metamorphized, whereas limestone can morph into marble.
The Geologic Column
In the origins debate, sedimentary rocks are especially important because they often contain fossils. From these we can learn something about the organisms of the past. Since the sediment was deposited by moving fluid, sedimentary rocks are often found in large horizontal layers, one on top of the next like a sequence of blankets. These are strata. Each layer seems to represent the material that was deposited continuously, with breaks in deposition separating layers. In places where the rock layers have been vertically cut, such as in the Grand Canyon, it is very easy to see these horizontal layers and to distinguish one from the next by differences in color and texture.
The horizontal layers are easily visible in the Grand Canyon
Geologists classify the fossil-bearing sedimentary rock layers into twelve major systems: Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian, Triassic, Jurassic, Cretaceous, Tertiary, and Quaternary. There is a statistical vertical order to these systems. For example, if both Jurassic and Cretaceous rock layers are found in a particular area, the Cretaceous layer will generally be on top of the Jurassic. Therefore, textbooks often depict these systems in a vertical sequence with Cambrian at the bottom and Quaternary on top. This is called the geologic column.
Most places on earth do not contain the entire geologic column. For example, you won’t find Jurassic or Cretaceous strata in Ohio. But you will in Utah. The geologic column is therefore a mental construct based on the observation that rock layers tend to occur in a particular order. Secular geologists believe that these systems represent different periods of time in earth’s past, each representing many millions of years. As such, they will often refer to things like the “Jurassic period.” But in terms of observational data, the Jurassic is a lithographic system – a rock layer.
Systems are grouped into larger blocks called erathems. The Cambrian through Permian systems belong to the Paleozoic erathem, Triassic through Cretaceous belong to the Mesozoic, and the Tertiary and Quaternary layers belong to the Cenozoic. There are subdivisions of systems as well. Most strata are continental in scale; they can be traced continually over most, but not necessarily all of a given continent.
Interestingly, fossils of some creatures are present in only some systems and absent in others. Dinosaur fossils, for example, are found only in Mesozoic layers: the Triassic, Jurassic, and Cretaceous systems. Trilobites are found in all the Paleozoic systems: Cambrian all the way through Permian. But they are not found in any higher layers. When a given organism is found in only one system, it is called an index fossil because it can then be used to identify that system if found in other regions. The lower systems contain only fossils of marine organisms, but the higher layers contain a mix of both marine and terrestrial organisms. Fossils below the Cambrian system are rare, and are primarily microbes.
Whereas secular geologists interpret the fossil-bearing strata as representing vast ages, creation scientists interpret most of them as progressive stages of the global flood. The Cambrian system seems to represent the initial stages of the flood. Systems below the Cambrian are thought to be pre-flood layers that were likely formed when God created the Earth and separated the land from the water. There is some debate as to which layer represents the last stages of the flood, but nearly all agree that it extends at least through the Cretaceous, and perhaps well into the Tertiary. The upper Tertiary and Quaternary systems are thought to be post-flood.
In 1858, Antonio Snider-Pellegrini proposed that the continents were not always separated as they are today. He argued on the basis of fossil evidence that they were originally connected into a supercontinent, and were pushed apart during the global flood. The fossil and lithographic evidence for this is quite compelling. For example, fossils on the east coast of South America match those on the west coast of South Africa. Furthermore, the shape of the continents is such that they do fit together, like separate pieces of a jigsaw puzzle. When connected, the rock layers and fossils match nicely. Creation scientists today largely agree that Snider-Pellegrini was right.
However, most geologists at the time dismissed the idea. The notion that something as large as a continent could move may have been difficult to accept. And the mechanism was unknown at the time. Later research supported the notion of plate tectonics: that earth’s crust is divided into a number of movable plates that essentially float on earth’s mantle. The boundaries between plates are marked by regions of volcanos and earthquakes, sometimes called the Ring of Fire. Collision between plates can cause mountain chains. Plate tectonics provides a credible mechanism for the separation of the continents and the formation of mountain ranges that occurred during the global flood.
But the theory of plate tectonics and continental drift did not catch on until the late 1960s. And secular geologists had to modify the idea to accommodate their belief in vast ages. Rather than breaking up at the time of the global flood, they proposed that the plates gradually drifted apart over millions of years. So creation geologists and secular geologists largely agree on the mechanism of plate tectonics, continental drift, mountain building, and volcanos. They simply disagree on when these events occurred and how quickly they took place.
Interpreting the Data
When attempting to reconstruct past events, scientists inevitably rely upon certain presuppositions to help them make sense of the data. We all agree on data. We agree that fossils are found in sedimentary rock layers, that these layers are deposited on continental scales, and that there is an order to the rock layers. We agree that the Earth was quite different in the past, and that fossils and rock layers reveal this information. But our presuppositions differ. And so we draw different conclusions regarding how and when these past events took place.
The secular view is driven by the philosophy of uniformitarianism. The belief is that present rates and processes are largely the same as past rates and processes. The uniformitarian motto is “the present is the key to the past.” Secular geologists assume that the rate at which mountains were pushed up in the past is similar to the miniscule rate at which they are being pushed up today, and that canyons have always eroded at about the same small rate they are being eroded today. They assume that since the continents are moving only very slowly today, that this was always the case. If these assumptions are true, then it must have taken millions of years for mountains to form, for canyons to form, and for the continents to have drifted at their current slow rate to their present positions after splitting apart from the original supercontinent.
On the other hand, creation scientists reject the belief in uniformitarianism and instead believe that most of Earth’s geological features were produced rapidly, during the creation week and during the global flood. During these events, the rate at which sediment was deposited, and the rates of mountain-building and canyon formation would have been immensely greater than the rates today. Under such catastrophic conditions, there is no need for millions of years. Any residual continental drift, mountain building, and canyon erosion that takes place today would be infinitesimal compared to the rates that took place during the flood year. Therefore, we may not blindly extrapolate from present rates conditions to past rates and conditions. For biblical creationists, the Bible is the key to the past, the present, and the future.
Most people have been taught the secular interpretation of the data, and are unaware of the biblical creation interpretation. But the data are exactly the same. It is not as though creationists have one set of fossils and secularists have a different set. We are all looking at the same rock layers, fossils, canyons, and mountain ranges. But our differing philosophical interpretive frameworks drive us to draw very different conclusions from the same data. Can we rationally determine which view is the correct one? Are the geological data equally compatible within both frameworks? If so, is there some other way to determine which view of origins is the correct view? In our next article we will answer these questions.
 In contrast, consider the historical details the Bible provides regarding the origin of the celestial bodies beyond the solar system: “He made the stars also.” (Genesis 1:16)
 Outside of North America, the Mississippian and Pennsylvanian are often treated as one combined system called the Carboniferous.
**** Part 2
In part one, we examined the basics of geology, and found that scientists generally agree on the observational aspects of geology regardless of their respective positions on origins. Creation geologist and secular geologists largely agree on the composition of rocks, where they are found, the way they are formed today, plate tectonics, the nature of strata, and so on. But when it comes to interpreting geological events of the past, we form different conclusions on the basis of different starting presuppositions and views of Earth history.
Secular geologists are largely driven either consciously or unconsciously by the philosophy of uniformitarianism. This view is the belief that present geological rates and conditions are largely indicative of past rates and conditions: “the present is the key to the past.” For example, today the rate at which the Grand Canyon is being eroded by the Colorado River is quite slow. The uniformitarian assumption is that this has generally been the case throughout Earth’s past – that the erosion rate has always been roughly what it is today. Assuming that there was no canyon to begin with, it would take a very long period of time for the Colorado River to cut a canyon as deep as the Grand Canyon at its present rate – much longer than 6000 years. Therefore, if uniformitarianism is true, then the Earth must be very old.
We must understand that uniformitarianism is a matter of degree. Most processes can be extrapolated at their present rate into the future or past to a certain extent and produce an accurate answer. For example, if a flower is observed to grow one millimeter per day, it is reasonable to think that in one week it will be about seven millimeters taller. But it is unreasonable to extrapolate this indefinitely. For example, we cannot conclude that in one hundred years, the flower will be thirty-six meters tall! There are limits to almost any extrapolation. The larger the extrapolation, the more likely the answer will be in error.
How far back can we accurately extrapolate using the assumption of uniformitarianism? We can do so until the last substantial change in rates. The problem is this: we usually don’t know when the last substantial change in rates was. Alternatively, in some cases we do know when it was due to recorded history; but not everyone embraces recorded history. For example, if we wanted to know how deep the Grand Canyon was in some previous year, we could extrapolate based on its current erosion rate and that would give a pretty reasonable answer – until we get back close to the year of the global flood. The runoff from the flood would cut a canyon much faster than the Colorado River ever could. And we know from recorded history that the flood occurred approximately 4,400 years ago. Any extrapolation from present rates beyond that date would therefore give an erroneous answer. But secular geologists generally reject the recorded history of the global flood, and continue to extrapolate based on present rates beyond the flood year into a fictional past. For this reason, their estimate of the age of the Grand Canyon is vastly inflated.
In contrast to uniformitarianism is the philosophy of catastrophism. Catastrophism acknowledges that Earth’s geological features can form quickly under rates that are far faster than typical rates in the present. We know, for example, that canyons do not need millions of years to form, because we have seen it happen. When Mount Saint Helens erupted in 1980 and afterwards, it devastated a nearby lake and deposited many new layers of sedimentary rock. It then cut through them forming a canyon roughly 1/40th the scale of the Grand Canyon. This happened in a matter of days. The event was observed and is well documented. So we know for certain that rock layers do not require millions of years to form, nor do canyons. And Mount Saint Helens was just one volcano. It is insignificant when compared to the global flood. Clearly, if catastrophism is true, then the Earth need not be very old and its geological features have formed quickly.
Of course, knowledgeable uniformitarian geologists will concede that catastrophes can indeed produce features at accelerated rates, just as creation geologists agree that uniformitarianism often gives reasonable answers when extrapolations are short. So, let us precise our definitions. A uniformitarian believes that the majority of Earth’s geological features were produced primarily by the kinds of slow-and-gradual processes that occur in the present. A catastrophist believes that the majority of Earth’s features were produced primarily under catastrophic conditions, far faster than rates that are typical in the present. In particular, biblical creationists believe that most of Earth’s geological features were formed during the creation week and the global flood.
Clearly, both uniformitarianism and catastrophism are presuppositions. They are each a philosophical pre-commitment in light of which geological data are interpreted. Therefore, the debate between these two systems of thought cannot be conclusively settled on the basis of geological data. That may seem ironic to people who are unfamiliar with epistemology. But since these respective presuppositions control our interpretation of the geological data, clearly the data cannot conclusively judge which interpretive system is correct. We will need to some other way to judge the relative strength of each system of thought.
The creationist has a very good reason to embrace catastrophism; recorded history. The Bible is primarily a history book, one that has demonstrated itself to be accurate time and again. Archeology has confirmed many of the events of the Bible. And the Bible records a worldwide flood. In fact, hundreds of flood legends from all around the world verify various aspects of the Genesis flood. In contrast, the secularist really has no good reason to embrace uniformiarianism. It is certainly not verified historically; we have no records of mountains or canyons forming over millions of years. Nor is it something that can be scientifically verified in the present, due to the length of time involved. That is, no one can observe or repeat in the present a canyon taking millions of years to form. As far as I can tell, secularists believe in uniformitarianism on blind faith.
But such discussions are not the purpose of this article. This is a geology article. Most geologists have been trained to interpret data in light of uniformitarianism – a philosophy that is blindly assumed. As such, most people have not considered the merit of biblical presuppositions in interpreting geological data. The geological facts make sense in light of biblical history.
The layers of strata that creationists believe were deposited during the global flood (Cambrian through at least the Cretaceous and possibly much of the Tertiary) are continental in scale. For example, the Tapeats sandstone is a Cambrian layer that is exposed near the bottom of the Grand Canyon. But this same sandstone covers much of the United States and Canada continuously. In other words, you could draw a path on a map of North America from the Grand Canyon up into Canada and, depending on the path, every part of it would have the Tapeats sandstone under it. Note that the same sandstone may be assigned a different name in different parts of the continent, but it is the same rock deposit. Therefore, whatever event or events deposited this sediment must have been continental in scale.
This is significant because we do not observe continental-scale deposits occurring today. Local floods will deposit sediment. But the extent of the sediment is limited to the extent of the flood. Nor can the Tapeats sandstone be the result of multiple small-scale floods because if time occurs between two floods, there will be some erosion from the sediment deposited by the first flood, producing a visible break in the rocks that are produced. Yet, the Tapeats sandstone is continuous in the regions in which it is found. Apparently, it was deposited by a flood that covered at least the majority of the continent of North America. This is consistent with the global flood described in Genesis 6-8.
But the Tapeats sandstone is just one part of the Cambrian system. What about the other rock layers? Which of them are continental in scale? The answer is: all of them. All the Paleozoic and Mesozoic layers are continental in scope: those systems that creation geologists believe to be flood layers. You can find rock layers in eastern states that are continuous with rock layers found in the Grand Canyon. These continental scale deposits just don’t occur today, and therefore should challenge the notion that the “present is the key to the past.”
This does not mean that every part of a continent has every system. The flood occurred in stages, and the earliest stages would not have covered the high ground. So by analyzing where the various systems are found, we can reconstruct the approximate topography of the continents as they were before the global flood. Central Africa, for example, is missing many of the lower layers, and therefore must have been high ground before the flood. The eastern United States does have these lower layers, indicating that it flooded early and must have been at low elevation before the global flood.
The Existence of Fossils
The sedimentary rock layers associated with the flood are full of fossils – mineralized remains of organisms. Most organisms never become a fossil. When they die, they decay or are scavenged, and their physical body is recycled back into the environment. Fossilization occurs when a dead organism is rapidly buried in sediment that hardens into rock. Usually the soft parts of the organism have time to decay, leaving the bones. Bones are porous and become mineralized; the water surrounding the bones contains minerals which move into the bones filling in the pores. A fossilized bone is therefore much heavier than a non-fossilized bone. Sometimes the fossilization process happens so quickly that even the soft parts of the organism fossilize. I have seen fossils of jellyfish.
The strata are full of fossils. But fossilization is not common today, and is never observed on a continental scale. This suggests that these fossil beds were produced by a continent-covering catastrophe, unlike the slow, gradual, and local deposition that takes place in the present. For a fossil to form at all, it must be buried rapidly, and completely. This challenges the notion that fossil-bearing sedimentary rock layers were deposited very slowly over millions of years. If it took millions of years to cover an organism in sediment, it would have had plenty of time to decay or to be scavenged.
Some organisms are so well preserved in the strata that some of the original material remains. Dinosaur remains have been discovered with evidence of red blood cells still inside the blood vessels which are still elastic. This strongly challenges the notion that these remains are millions of years old. It is not realistic for soft tissue to survive that long.
Furthermore, in some cases, sufficient original material remains for the specimen to be carbon-dated. Inevitably, the estimated ages turn out to be a few thousand years – never millions. Carbon dating is based on detecting C-14 atoms. C-14 has a half-life of 5730 years and cannot last even one million years. Yet scientists routinely find C-14 in the remains of organisms buried deep in the rock strata. This also challenges the notion that these rock layers are millions of years old. How could a millions-of-years-old rock contain a thousands-of-years-old fossil?
The Types and Order of Fossils
The very existence of fossils deposited on continental scales suggests a worldwide flood. But the types of fossils we find and their order confirm this. What would be the first organisms to be buried in sediment in a global flood? It would not be land organisms. They would flee to higher ground and there would not yet be sediment to deposit on them. The flood waters would collect sediment from the land and dump it into the sea. The sediment would settle at the lowest elevations first. So the first organisms to be buried would be ocean-dwelling creatures. And what do we find? The lowest fossil-bearing strata contain ocean-dwelling organisms. The Cambrian system contains fossils of clams, worms, sponges, starfish, fish, as well as marine organisms that are now extinct such as trilobites. What do all these organisms have in common? They live in the ocean. They would be the first to be buried, and therefore found in the lowest strata – which is exactly what we find.
Sometimes evolutionists misrepresent the biblical position and claim that the global flood would produce no order in its deposits. But this is unrealistic. The flood occurred progressively, advancing to higher ground over time according to passages such as Genesis 7:17-20. The global flood (both the advancement and recession stages) lasted many months. Noah and his family were aboard the ark for over a year. Given this gradual progression, of course the lower animals will be buried earlier and in lower layers than those animals that live inland and at higher elevations. The evolutionists complain, “If there was a global flood, then why don’t we find rabbits in the Cambrian?” The answer is obvious: rabbits don’t live in the ocean.
Second, note where these fossils of ocean organisms are found: on land! The Cambrian strata covers much of the United States and Canada, indicating that this continent was once under water. Other continents are also covered in marine fossils, even on the highest mountain tops. It is difficult to avoid the conclusion that Earth once experienced a global flood.
As we go to higher strata, we find organisms that lived in progressively higher ecological niches, eventually including land plants and animals. Note that while the lower layers contain only water-dwelling organisms, the higher layers contain both land and ocean creatures together. I have seen a deposit that has both a small dinosaur and a fish buried next to each other. What kind of event would bury land animals with ocean animals? As the flood waters progress to higher ground, they would eventually overtake land animals, but marine creatures would be mixed in as well as they are carried with the flood waters. Organisms that reached the highest ground are unlikely to fossilize because there would be no additional sediment available to cover them. Unprotected from the elements, they decayed back into the environment.
Secular scientists require vast ages because they recognize that Darwinian evolution cannot happen within the biblical timescale. (Actually, it cannot happen in any timescale – but that’s a different topic). So they are committed to a uniformitarian scenario, regardless of all this apparent evidence to the contrary. And they do offer arguments against the biblical flood. But usually, a careful examination of the presented evidence turns out to challenge the uniformitarian view, and confirms the biblical flood. One spectacular example of this concerns the Coconino sandstone, which is one of the higher layers visible in the Grand Canyon. Secularists used to claim that this layer was evidence against the global flood.
Secular geologists once proposed that the Coconino sandstone represented an ancient desert. This would allegedly pose a problem for the global flood since the Coconino is sandwiched in between the Hermit formation and Toroweap formation – both of which are deposits of the global flood. So how do you get a desert to form during the middle of a global flood? More importantly, what is the evidence that this was an ancient desert? Two lines of evidence were presented.
First, the Coconino sandstone has cross-bedding: layers within a stratum that are at an angle relative to the main bedding plane. Geologists began to interpret such crossbedding as the result of sand dunes; modern sand dunes have inclined internal sand beds due to the way the wind picks up and deposits the sand grains. Second, the Coconino sandstone has a large number of footprint sequences called trackways. They were apparently made by four-footed terrestrial vertebrates (reptiles or amphibians). These were interpreted as footprints of animals as they crossed the dunes in the desert.
Is this evidence against the global flood? More recent research has shown that cross-bedding is not limited to desert sand-dunes, but can also form under water as sand-wave deposits. However, the angle of cross-bedding is somewhat lower than that of desert dunes. The Coconino sandstone has an average cross-bedding angle of 25 degrees, which is consistent with the angle for sand-waves deposited by water. But desert sand dunes tend to have a higher angle, often exceeding 30 degrees.
Second, the footprints in the Coconino sandstone are quite distinct – individual toe marks are often visible. Have you ever seen distinct footprints in dry sand? Neither have I. Dry sand may leave a depression, but the sand collapses around the edges eliminating details. Wet sand, however, can leave a very detailed footprint. You can confirm this yourself by walking along a beach, first in the dry sand, and then in the wet sand closer to the surf.
Our intuition was scientifically verified by Dr. Leonard Brand of Loma Linda University who performed experiments in which he measured footprints of reptiles and amphibians as they occur under water, on moist sand, and on dry sand respectively. His results show that the Coconino sandstone trackways best matched those footprints that were made under water.
Interestingly, the Coconino trackways all seem to be going uphill; the toe impressions were far more distinct than the sole impressions, as if the animals were trying to go uphill. Furthermore, the direction of the trackway is not usually the direction the animals’ toes were pointed – as if the animal was attempting to move in one direction, but was being carried by water current in a different direction. All in all, the evidence for the Coconino being a water-deposit is quite compelling.
Much more could be stated (and has been documented in other works) in support of the global flood on the basis of geology. But even in these introductory articles, the evidence is quite overwhelming. In summary, (1) the Paleozoic and Mesozoic rock layers are continental in scale, which is consistent with a global flood but inconsistent with the numerous local floods that occur today. (2) Fossils always indicate rapid burial, and the sedimentary layers are full of them. This is consistent with the Genesis flood, but inconsistent with slow-and-gradual deposition over millions of years. (3) The types of fossils we find are consistent with a global flood; namely, we find fossils of marine organisms on land. Furthermore, the order in which we find these fossils is precisely what would be expected as the flood progressed. (4) Layers such as the Coconino sandstone bear striking evidence of organisms attempting to flee while being carried by water.
In light of such scientific evidence, it may be hard to believe that some people continue to deny the global flood. But this obviates the truth that presuppositions control our interpretation of all evidence. And it also reminds us that the debate is not merely one of scientific models. There is a spiritual issue as well. The global flood reminds us that God judges sin. And we are sinners. It is an uncomfortable thought that God is rightly angry at us for our rebellion, and that judgment is coming. The unbeliever is inclined by his sin nature to suppress this truth in unrighteousness. It’s not surprising that unbelievers deny God’s judgment of water; they also deny His coming judgment of fire.
The Bible predicted all this. God knew that people would deny the second coming of Christ, would embrace a belief in uniformitarianism and deny that the world of man was once destroyed by a global flood. This is all predicted in 2 Peter 3:3-6. So by denying what the Bible says in Genesis 6-8, unbelievers prove the Bible is true in 2 Peter 3:3-6! Geology reminds us that God is a righteous God and will therefore not tolerate sin indefinitely. And yet the fact that we are here proves that God is also merciful; God warned Noah and instructed him on how to prepare for the coming judgment so that he and his family would live. Today, God again warns us of His coming judgment, and encourages us to call upon Christ to be saved.