What is a Fossil?Fossils are the remains of organ-isms or other signs of organisms that lived in the past. For exam-ple bones, or shells. Ichno fossils (trace fossils) are for example tracks, bite-marks, and excre-tions. These ichno fossils can teach us a lot about the organ-ism. Fossils are often petrified. This takes place as a result of chemical mineralization process-es.

The best-preserved fossils form when the organism is quickly buried. If the organism is not buried quickly, external factors such as scavengers, decay and the weather can deteriorate the quality of the fossil to be. The right conditions for fossilization are exceptional. In most cases an organism will not fossilize. If the organism is buried in an anoxic environment, even the soft parts can be preserved. Mostly only the harder parts, such as shells or skeletons, are fossilized.

The fast burial of organisms occurs mainly in sediments of watery environments (i.e. clay, sand in rivers and oceans). Fossils of land animals are more rare. On land you need for example a volcanic eruption or flashflood to bury the organism fast enough with sediment.

After burial it depends on the chemical composition of the sed-iment whether the organism is well preserved or not. In the sed-iment chemical and mineralogical composition of the fossil can be altered. The internal structure re-mains preserved. Otherwise the fossil can be dissolved in water. In this instance the cavity can later be filled up by another mineral.

There are three types of rocks: Igneous rocks, Metamorphic rocks and sedimentary rocks. Igneous rock form by the cooling of magma. Metamorphic rocks form by exposing already exist-ing sediments to high temper-atures or pressure (deep in the earth’s crust). Fossils only occur in sedimentary rocks which are described below.

Most sedimentary rocks are formed when erosion products are deposited in layers, and over time lithifies into rock. Erosion products are the materials that form during erosion of rocks by water, ice, wind, etc. This is how conglomerates (pebble stone), sandstones and shale’s form. These rocks are ultimately ero-sion products of igneous rocks.

Other sedimentary rocks do not originate from erosion products. For example, peat can compact and lithify into coal. Limestone forms when little chalk skeletons of sea organisms sink to the sea-floor. Under special circumstanc-es some sedimentary rocks can form by precipitation of dissolved chemicals from the seawater. For example gypsum and rocksalt.

Time, high pressure (when sed-iments are buried deep in the earth’s crust), and high temper-ature will cause loose sediments to lithify into rocks. This is the result of compaction and sev-eral chemical processes in the sediment. When sediments are buried deep inthe earth’s crust, or exposed to high temperatures, new types of rocks can be formed as a result. Geologists are always on the lookout for sedimentary structures to reconstruct the environment during the forming of the deposit.

There are three types of rocks: Igneous rocks, Metamorphic rocks and sedimentary rocks. Igneous rock form by the cooling of magma. Metamor-phic rocks form by exposing already existing sediments to high temperatures or pressure (deep in the earth’s crust). Fossils only occur in sedimen-tary rocks which are described below.

Most sedimentary rocks are formed when erosion products are deposited in layers, and over time lithifies into rock. Erosion products are the mate-rials that form during erosion of rocks by water, ice, wind, etc. This is how conglomerates (pebble stone), sandstones and shale’s form. These rocks are ultimately erosion prod-ucts of igneous rocks.

Other sedimentary rocks do not originate from erosion products. For example, peat can compact and lithify into coal. Limestone forms when little chalk skeletons of sea organisms sink to the seafloor. Under special circumstanc-es some sedimentary rocks can form by precipitation of dissolved chemicals from the seawater. For example gypsum and rocksalt.

Time, high pressure (when sediments are buried deep in the earth’s crust), and high temperature will cause loose sediments to lithify into rocks. This is the result of compac-tion and several chemical pro-cesses in the sediment. When sediments are buried deep in-the earth’s crust, or exposed to high temperatures, new types of rocks can be formed as a result. Geologists are always

"Fossils A Evolution In the making"

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Some animals were quickly buried after their death (by sinking in mud, being buried in a sand-storm, etc). Over time more and more sediment covered the remains. The parts of the animals that didn’t rot (usually the harder parts like bones and teeth) were encased in the newly formed sediment. In the right circumstances (when there is no scavengers, quick burial, not much weathering) parts of the animal turned into fossils over time. After a long time the chemicals in the buried animals bodies underwent a series of changes. As the bone slowly decayed, water infused with minerals seeped into the bone and replaced the chemicals in the bone with rock-like minerals. mineral changes its form).