Studying the Past Fossils, Relative Time and Absolute Time

Paleontology The study of the forms of life existing in prehistoric or geologic times, as represented by the fossils of plants, animals, and other organisms.

What do you know about fossils?

Fossils Fossilis is Latin for “dug up” Fossils are the remains, molds or traces of organisms that died a long time ago Fossils are usually found in sedimentary rock like sandstone, limestone or shale

Fossils Fossils provide evidence that different organisms lived long ago Fossil organisms many times do not exist on Earth anymore They have gone extinct or they have evolved They have gone extinct or they have evolved

Fossils As we go through the different types of fossils look for what each type of fossil needs to form.

5 Main Types of Fossils Original Remains Replaced Remains Molds and Casts Trace Fossils Carbonaceous Films

Original Remains Very rare Most animals decay or decompose Most animals decay or decomposeExamples Frozen woolly mammoths Frozen woolly mammoths Insects incased in resin (amber) Insects incased in resin (amber)

Replaced Remains Actual remains are replaced with minerals Many hard parts fossilize this way Teeth Bones Shells

Molds and Casts A replaced remain fossil may dissolve leaving behind a mold Later minerals may fill in the mold creating a cast of the original organism Click picture to see cast and mold formation

Trace Fossils No actual part of the organism is left Give information about the location of different organisms Traces like Impressions Impressions Bite Marks Bite Marks Burrows Burrows Feces Feces Tracks Tracks Coprolites Coprolites

Carbonaceous Films An imprint or thin film is left behind Not the actual organism Tissue undergo chemical changes

What do fossils need to form? SedimentCompactionWaterMineralsOrganism TIME!!! Lots of TIME!!!

Fossil Concept Map 1. Write in the 5 fossil types 2. Write in a few details about each fossil type

What Do Paleontologists Study? 1.Global warming 2.Prehistoric life 3.Future life 4.Rocks Only 5.Plants Only

Why Would Fossils Not Be Usually Found In Igneous Rocks? 1.They are older than igneous rocks 2.Forming igneous rocks would destroy fossils 3.All igneous rocks are found deeper than fossils

If you found the tooth of a Tyrannosaurus Rex, you found a… 1.Original Remain 2.Replaced Remain 3.Mold/Cast 4.Trace Remain 5.Carbonaceous Film

Dino dung is a… 1.Original Remain 2.Replaced Remain 3.Mold/Cast 4.Trace Remain 5.Carbonaceous Film

A dark imprint of a leaf is a… 1.Original Remain 2.Replaced Remain 3.Mold/Cast 4.Trace Remain 5.Carbonaceous Film

If a shell creates an air pocket with its exact shape in sedimentary rock, it is a… 1.Original Remain 2.Replaced Remain 3.Mold/Cast 4.Trace Remain 5.Carbonaceous Film

The mosquito that gave the scientists the DNA necessary to create dinosaurs in Jurassic Park was a… 1.Original Remain 2.Replaced Remain 3.Mold/Cast 4.Trace Remain 5.Carbonaceous Film

Dating Past Geologic Events Relative Dating Example: Example: On the way home I stopped for gas First, I ate dinner I drove home Then I went to the store Absolute Dating Example I drove home at 5:35 I stopped for gas at 5:25 I ate dinner at 5:00 I went to the store at 5:15

Dating Past Geologic Events What is the difference between these two dating methods? Relative Time has no actual times but can be put in order Relative Time has no actual times but can be put in order Absolute Time gives actual times Absolute Time gives actual times

Relative Time Puts events in a sequence without telling when they actually happened Does not reveal actual age but age in comparison to other events

Relative Dating The evidence is in the rocks Each layer represents a different place in time Every layer of rock is another part of the timeline

Uniformitarianism “the present is the key to the past” We can watch how things happen now to understand how they happened before. We can watch how things happen now to understand how they happened before.

Uniformitarianism James Hutton realized these processes did not happen quickly therefore the Earth must be very old.

Uniformitarianism Siccar point in Scotland is where he made the observations Came up with the idea of DEEP TIME

Principles of Relative Dating Principles of Relative Dating The Principle of Superposition The Principle of Cross-Cutting Relationships Embedded Fragments

The Principle of Superposition Draw This… Water

The Principle of Superposition The OLDEST rock is on the bottom and the YOUNGEST is on the top Rocks are deposited horizontally

The Principle of Cross-Cutting Relationships Draw This… Water 4

The Principle of Cross-Cutting Relationships An igneous intrusion is YOUNGER than the rock it intrudes A fault is YOUNGER than the rock it breaks

The Principle of Embedded Fragments Water 4

Rocks that are embedded in other rocks are OLDER than the rock they are found.

Unconformity Gaps in time Surfaces have been eroded away New rock has been laid on top

Unconformity

Putting in all together Rock layer correlation Matching rock in one area to rocks in another Matching rock in one area to rocks in another Match characteristics Match index fossils Using fossils to tell what type of environment existed

Index Fossils Fossils that can be used to identify a certain rock layer Fossils that lived within a certain time can give the rock a relative age. See page 653

Fossils Fossils can also give clues to the type of environment existed. Is there a lot of coral? Is there a lot of coral? Are there a lot of amphibians? Are there a lot of amphibians? Are there a lot of deep sea animals? Are there a lot of deep sea animals?

Relative Time Use the present to determine past processes No actual time is given Fossils can be used to indicate a general time 3 Principles

What is relative dating? 1.Assigning an actual age to something 2.Putting events into order 3.Going out with your cousin

What is absolute dating 1.Assigning an actual age to something 2.Putting events into order 3.Going out with your cousin absolutely

What is uniformitarianism? 1.Fossils all form the same way 2.All layers of sediment form horizontally 3.The rules of nature have always been consistent

What is the principle of superposition? 1.The oldest rock is on the bottom and the youngest is on the top 2.An igneous intrusion and fault is younger than the rock it intrudes 3.Rocks that are embedded in other rocks are older than the rock they are found.

What is an unconformity? 1.A gap in the geologic timeline 2.A rock that is out of place 3.A punker or goth

What is an index fossil? 1.A fossil that lived in the Jurassic 2.A fossil that is a replaced remain 3.A fossil of an animal who’s time period is known