WHAT’S IN THE ROCKS!

Bell Work If you were to put the following events in to a time sequence of first to last, how would you do it? What else would you add?  Go to school  Wake up  Eat lunch  Put clothes on

State Performance Indicators  SPI Compare fossils found in sedimentary rock to determine their relative age

Objectives  Describe the process of relative dating to determine the age of rocks  Apply geologic principles by using fossils to date sedimentary rocks  Compare and Contrast different types of fossils in sedimentary rock to determine their relative age

Sedimentary Rock cover of the Earth’s land area.  Sedimentary rocks cover 75% of the Earth’s land area.  Layer after layer of eroded earth is on top of each. Theseare pressed down more and more through time, until the bottom layers slowly turn into.  Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.

Relative Dating Scientists use different methods to determine the age of objects in sedimentary rocks. One method, relative dating, examines a fossil’s position within rock layers to estimate its age.

 The bottom layers of rock are usually the oldest, and the top layers are usually the youngest.  Scientists can use the order of rock layers to determine the relative age of objects within the layers.

Discuss with elbow partner which layer is the oldest in this rock column and which is the youngest. Identify the type of rock in the oldest and youngest layers. Which is the biggest fossil in the rock column? Is the fossil young or old relative to the other fossils in the rock column?

The Geologic Column To make relative dating easier, geologists combine data from all of the known rock sequences around the world.

Paleontology Paleontology is the science involved with the study of past life. Scientists who study past life are called paleontologists. Paleontologists collect data by studying fossils.

A fish out of water! Future Fossil News Alert  This fish, a Senegal bichirs can walk – and “breathe” on land! Weird but true! weird but true !

Section 2 Looking at Fossils

 The remains or physical evidence of an organism preserved by geologic processes is called a fossil.

 Fossils in rocks happen when organisms die, the fleshy parts decompose, and are buried quickly in sedimentary rocks.  The hard parts are left to become fossils.

 Fossils in a occur when insects get stuck in that quickly.  Fossils in amber occur when insects get stuck in tree sap that hardens quickly.

is the process in which minerals an organism’s  Petrification is the process in which minerals replace an organism’s tissues.  One form of petrification is called, which is the process in which fill pore spaces of an organism’s tissues (EX) bone, wood  One form of petrification is called permineralization, which is the process in which minerals fill pore spaces of an organism’s tissues (EX) bone, wood

occur when animals are frozen in ice and die. We find them 1000s of years later when it thaws.  Frozen fossils occur when animals are frozen in ice and die. We find them 1000s of years later when it thaws. occur when animals are preserved in thick, sticky pools of tar.  Fossils in Asphalt occur when animals are preserved in thick, sticky pools of tar.

are any naturally preserved evidence of an animal’s  Trace fossils are any naturally preserved evidence of an animal’s activity.  Three types: - footprint 1. Track- footprint shelters made by animals 2. Burrows- shelters made by animals preserved animal dung 3. Coprolites- preserved animal dung

 Discuss with your elbow partner why tracks and coprolites are considered trace fossils. Burrow Coprolite

 Some fossils do not contain any original material of the original organism. Molds form when sediments cover the organism, such as shell, and the hard part is later removed by weathering or erosion.

 A cast is an object that is created when sediment fills a mold and becomes rock.

History of Changing Organisms Scientists study the relationships between fossils to interpret how life has changed over time. Since the fossil record is incomplete, paleontologists look for similarities between fossils over time to try to track change Since the fossil record is incomplete, paleontologists look for similarities between fossils over time to try to track change.

Using Fossils to Date Rocks Scientists have found that particular types of fossils appear only in certain layers of rock.

 By dating rock layers above and below these fossils, scientists can determine the time span in which the organism lived.  If the organism lived for a relatively short period of time, its fossils would show up in limited layers.

are fossils of organisms that lived for a relatively short, well defined geologic timespan. Index fossils are fossils of organisms that lived for a relatively short, well defined geologic timespan. Trilobites

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