Take out your spiral notebook Earth History Take out your spiral notebook

Sedimentary Rock Many thousands of layers of sedimentary rock provide evidence for the long history of earth and for changing life forms whose remains are found in the rocks. Deposited rock layers are more likely to contain fossils resembling existing species.

Earth Processes The earth processes we see today, including erosion, movement of lithosphere plates, and changes in atmospheric composition are similar to hose that occurred in the past. Earth’s history is also influenced by occasional catastrophes, such as the impact of an asteroid or comet.

Plate Tectonics http://www.brainpop.com/science/earthsystem/platetectonics/

Changing Surface Thousands of layers of sedimentary rock confirm the long history of the changing surface of the earth and the changing life forms whose remains are found in successive layers.

Layers The youngest layer are not always found on top, because of folding, breaking, and uplift of layers.

Fossils Fossils that can be used to help determine the relative age of rock layers are called index fossils Relative age describes the age of an object or event in comparison to another object or event.

Fossils http://www.brainpop.com/science/diversityoflife/fossils/

Absolute Absolute geological dating and relative geologic dating are two methods by which scientists try to determine the age of geologic evidence. Carbon-14 dating is an example of absolute dating, and law of superposition is an example of relative age.

Carbon Dating http://www.brainpop.com/technology/scienceandindustry/carbondating/

Radioactive Dating Radioactive dating is used to study the uranium in igneous and metamorphic rocks. Uranium is mildly radioactive substance that breaks down at a slow and steady pace which cannot be altered by temperature or pressure.

Age of Earth By looking at different rocks and comparing the amount of uranium still in the rock to the amount of lead that has been formed, scientists can measure the age of the earth. Using this method scientists have determined the earth is 4-5 billion years old.

Buried Sediments of sand and smaller particles are gradually buried and are cemented together by dissolved minerals to form sold rock again Sedimentary rock buried deep enough may be re-formed by pressure and heat, perhaps melting and recrystallizing into different kinds of rocks

Re-Formed Rocks These re-formed rock layers may be forced up again to become land surface and even mountains. This new rock too will erode Rock bears evidence of the minerals, temperatures, and forces that created it.

Rocks, Fossils, and Ice Cores Rocks, fossils and ice cores show Life forms have changed over time Earth climate and surface have changed over time

Law of Superposition The law of superposition states that each undisturbed rock layer is older than the layer above it. This law is used to read rock layers Thousands of layers of sedimentary rock confirm the long history of the changing surface of the earth and the changing life forms whose remains are found in successive layers

Geologic Time Scale By studying rocks and fossils, scientists have developed a geologic time scale which outlines the major divisions of earths history Geologists have concluded that all rocks of the crust form in one of three ways:

Geological Time http://www.brainpop.com/science/earthsystem/geologictime/

3 Ways Igneous rocks are formed by the cooking and hardening of hot molten rock from inside of earth Sedimentary rocks are formed by the hardening and cementing of layers of sediments. Sediments consists of rock fragments, plant and animal remains, or chemicals that form on a lake and ocean bottom

3 Ways 3. metamorphic rocks are formed when rocks that already exist are changed by heat and pressure into new kinds of rocks. A fault is fractured in the continuity of a rock formation caused by shifting or dislodging of the earths crust, in which adjacent surfaces are displaced relative to one another and parallel to the plane of fracture