 continuously changing planet. It's being formed by many geologic processes. It is trying to balance products and processes as it moves along. The geologic processes that we experience and sometimes we don't experience actually vary in terms of rates and intensities. Sometimes it's very fast like in volcanic eruptions. As you know, Mount Pinatubo erupted very, very violently in the past in 1991. And of course there are many landslides that people are experiencing very recently in Mexico for example. There are many landslides that are happening today affecting many of our lives. They're also very slow geologic processes such as sedimentation. This is the process by which particle by particle, grain by grain, sand and silt comes down from the rivers and all the way to the sea. So as you know, there are many, many examples that we can actually think of. And so as we go along, we know that geologic time is actually very, very long. It's something that we cannot imagine even in our lifetimes because many of the processes actually happen over many, many human lifetimes, over thousands and even millions of years. Fossilization is one of these processes. It is the process by which fossils which are traces and remains of organisms that have been buried in the earth for a very long time are actually preserved. Some of us know what fossils are. You've been to museums probably. You've probably studied it in your geology classes or earth science classes somewhere in high school. But many of us actually haven't seen fossils on rocks or in the rocks themselves. Many think that they're quite rare or actually some think they're common just like us. We think they're common things that we find on our planet, but many times you only see them in special places such as museums. Actually, you can just move around and look for fossils somewhere around the campus of UP. For example, we have many fossils of trees and roots and sometimes if you move further into Antipolo, we actually found elephant fossils there and some turtles as well. And these fossils are actually one to two million years old. Many Filipinos are not very familiar with fossils because we also do not have that habit of going to museums or studying about rocks and fossils every day. So fossils are actually very, very useful in many of the things that we that we see around us in trying to understand the age of the rocks around us in trying to look at the sequences of rocks and trying to determine which one is older and younger. We also use fossils in order to understand the history of the earth and the oceans. We use them to determine changes on the earth via plate tectonics. I don't know if you've heard about plate tectonics in your earlier earth science classes, but it's all about the movement of the plates or the lithosphere on the surface of the earth where continents and even ocean crust actually moves around, bumps into each other, slides past each, slide past each other, and so on. There are also many climate changes that have happened on the surface of the earth and many of these are actually determined by using fossils. Fossils are also used to support the theory of evolution. Biologists from Darwin's time have actually used the study of fossils in order to really determine that life has changed through time. We also use these fossils in order to look for minerals and energy resources on our earth, especially oil, gas, coal, and other hydrocarbon deposits. We usually use fossils also in our daily lives such as when we're trying to understand the past and also our present and trying to understand the future, for example. There's actually a basic tenet in geology called the principle of uniformitarianism, which states that the present is the key to the past. This actually means that geologic processes that happened in the past can be used to understand the geologic processes of the present. And usually when we look at fossils, we try to understand how these fossils were in the past, how probably the organisms that made these fossils behaved in the past by looking at their relatives in the present. In UP, where we study fossils, we usually go to the sea in order to look at the present-day relatives of these fossils. We go to the reefs, for example, of Matabunkai or the reefs of Bulinau in order to see all of the invertebrate organisms that are in the coral reefs. By looking at how they look like, their morphology, and looking at how they behave, we learn to understand how the fossils probably behaved also in the past, the fossils that we find in the rocks. Fossils are actually very important in order for us as humans to understand our place in history and our place in the scheme of things. So what are fossils? They're actually the remains or traces of organisms that have been buried in the earth for a very long period of time. Fossilization actually takes quite some time. You have to imagine that the soft tissues of the animal has to be decayed and sometimes that takes a very short time, like in minutes or hours, but sometimes it can also take several months or weeks. It also has to be transported because normally things on the surface of the earth actually are being transported away from where they were first deposited and as they are transported, the tissues of these organisms actually break. And afterwards, if they're lucky, these parts of the organisms can be buried and modified into harder tissues so that they can be preserved in the surface of the earth. There are many requirements. There are some requirements for organisms to be fossilized. First of course, it has to have a hard part. Sometimes it can be a shell, the bone, or actually the tooth, and other times it can be just being buried very, very quickly in a protective medium. Of course, you have to imagine that it can't be a boulder that will bury this particular fossil. It also has to be a very special condition whereby small particles are probably falling down on this particular dead animal or plant on the surface of the earth. One of the best ways by which a fossil can be buried is when it's under the sea in a marine condition where fine sediments such as mud or silk will rain down on these fossils. Also, it's very important for that fossil to actually have a preserving medium. And these preserving medium can be a special a star or asphalt, ice, for example, amber, which is a fossilized tree resin. And so sometimes these special protective media are very hard to find on the surface of the earth. There are certain types of fossilization. There are instances where no alteration happens or no change happens to the fossil. And so the original fossil itself or the original organism can be preserved. These are very special conditions. And we find these in the woolly mammoths, which are about a million years old. Some are as young as 25,000 years. Of course, in geology, thousands of years is still young. It's when it reaches about the million years or so when it's considered very old. So these woolly mammoths, actually, which were found in Siberia, were preserved wholly in the ice. So this is a very special condition. Sometimes cellulose in plants can also be preserved. The chitin or the hard covering of insects can also be preserved, such as when you, if you've seen cockroaches, and I know many of you have seen cockroaches, that crunchy part of the cockroach is what we call chitin, and it can be preserved very, very well as fossils. Also, sometimes cartilage in some vertebrates can also be preserved. Some inorganic compounds can also be preserved, such as the calcium carbonate in shells that we find in corals, in the pelsipods or the clams that we find, they can also be preserved without alteration. So the original appearance in morphology and the composition of the animal or the plant can be preserved. Most of the time there is a preservation with alteration, which means that the actual organism is changed as time goes on. So this is the more normal or the more common way by which fossilization happens. Organic compounds, such as the carbon in rocks, can be preserved. Sometimes the leaves of the fossils, such as what you see sometimes in museums, where the ferns are preserved in the rocks, the carbon in them can be preserved in carbonization. Sometimes also the hard wood in trees can also be preserved through petrifaction or permineralization. There is actually a big national park in the U.S. where preserved trees are found. Most often though, the chemical composition in the rocks or in the fossil itself is recrystallized. This means that less stable organic compounds alter in physical form to more stable state without change in the chemical composition. A prime example of this is the aragonite we find in corals today and in the gastropods or the relatives of the snails that we find today. Another way by which fossilization happens is when there is replacement. This means that the original material is replaced by a new material, such as calcium carbonate. Silica or other iron compounds takes the place of the original compound, which is usually calcium carbonate. This happens in shells most of the time, especially in cephalopods, which we call ammonites. Actually, another way by which fossils can be preserved is by becoming molds or casts. You can imagine this when you're baking a cake. The cake is the cast, whereas the mold is the pan from which your cake is being baked. The mold sometimes can form when the animal imprints itself in mud under the sea. Sometimes some of the inner parts of the fossil or that organism can be filled in by other particles around it, and that can form the cast. This is common among pellicipods again, the snails, and the clams that we see in the ocean bottom. There are also other interesting fossils which are called trace fossils, or we call them ikno fossils. These are preserved remains of the activity and behavioral patterns of the organisms. If you imagine a snail, for example, moving along the lawn of your garden, you'll see that there are traces sometimes that the snail leaves on the surface of the soil. These can be preserved in time as trace fossils. We see this in trilobites. They've been moving around on the ocean floors in the Paleozoic, for example, and we see their traces on the ground. We also have dinosaur footprints that are present in many of continental areas where the dinosaurs roamed during the Mesozoic. Sometimes also bird tracks can be found on the surface of the earth, and these can be preserved and it gives us a good example of how these organisms lived in the past. Sometimes also burrows can be formed where worms or organisms that bury in the sea bottom can leave their traces there as linear structures in the bottom of the sea. Sometimes also, interestingly, they're fossil feces. I know some of you are probably laughing right now, but they're called fossil dung, copper lights. They can be also preserved as fossils. They actually look very interesting. They actually don't have the smell of dung anymore. They actually smell very metallic because they've now turned into rock. And these fossil dung or copper lights can be used to determine what the animals ate and how they lived during the time when they were on the surface of the earth. Many dinosaurs left copper lights, turtles also left copper lights, and many other carnivorous animals also left copper lights on the surface of the earth. We can also find borings, bite marks, certain dinosaurs actually preyed on each other. And so sometimes we see bite marks also of marine reptiles on other marine reptiles as they lived on the surface of the earth. Another interesting kind of trace fossil is what we call as a gastrolith. Sometimes they're called stomach stones or gizzard stones, but actually they did come from the actual stomach of the organism itself. These are actually just rocks or pebbles that were left on the inside the stomachs of these dinosaurs or other reptiles or other animals that actually use them so that they can digest their food inside their stomach more effectively. Usually the grain size depends on the size of the animal. It can be anywhere from a sand size, a particle of rock to a cobble sized rock. So it can be as big as my fist, but usually it's very smooth and very polished. And the composition of the rock is very different from the surrounding rocks which preserve the particular animal. But why do we study fossils? Fossils are actually very important for us as geologists, for example, because we call them stratigraphic indicators. Stratigraphy is the study of the sequence of rocks. We have to determine which rocks are older or younger than another rock. And so fossils are used to determine the relative ages of these rocks and they're very good determinants. I, for example, study a particular microfossil called nanofossils and they're very effective up to about a million or even half a million year resolution in order to understand where the rock layers are actually positioned. We also study fossils, most especially for most of you, you're probably familiar with this from biology lessons in the past, that we use them to record past life. They show the course of evolutionary changes in animals and plants through time. This has been very well recorded in the fossil record from the Precambrian to the present, that we have simpler fossils earlier in time in the Precambrian in the form of green algae, whereas today we have humans in more advanced forms of organisms, more complex structures are found now in the present-day organisms that we find today. So we see this in the record of fossils. Some other important fossil finds, for example, the evolution of the horse, which was traced throughout the Cenozoic, show that actually horses range from the smaller sizes to the present sizes we have today, that you see actually on TV, in TV series or actually in race tracks, that they're actually a lot larger than they are today. In the past, they were actually smaller because there was no need for them to run around so fast and to have so legs that are very, very long. They are also evidences of changes that have happened in our climate because in the past, there was no reason for them to run faster because they were living in forested areas. Today, horses are more endemic or more native to areas where there are grasslands. And so they had to run faster, their eyesight had to be keener, and also more importantly, from evidences of how their teeth changed through time, their teeth had to be able to chew a lot of grass, which is full of silica and which is actually hard for them. And so the change in the climate, which led to the change in the types of plants that they were eating, can actually be traced in the bones and the teeth that the horses have evolved through time. We also study fossils in a big way so that they can be used as clues or evidences of changing environments and geographic patterns through Earth history. We see this in plate tectonics. Some of you are probably familiar with it from earlier Earth science lessons. Plate tectonics is the movement of the lithosphere of the plates on the surface of the Earth. Sometimes they bump into each other, sometimes they sink underneath each other or they slide past each other. And we know the movement of the plates by using fossils. Also one of the main evidences that was used to prove plate tectonics was actually by the use of fossils. We also use fossils in order to understand climate change through time. In the fossils that we study in the marine realm, we see that many of these fossils change. The types of fossils that we see in the rocks change actually when there's warm climate versus colder climate. When the currents change, we also see these evidences in the fossils that we have.