Fossil Records and Index Fossils

The Fossil Record

​Fossils and Ancient Life

​Extinct - All populations around the world of that species have died out

​Fossils - Extremely rare due to the certain conditions needed for formation

​Shells, bones or teeth compounds are slowly replaced by minerals and harden

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Sedimentary Rock - The only rock fossils can really form in

​Igneous Rock - The heat will destroy the fossil

​Metamorphic Rock - The heat and pressure will destroy the fossil

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Multiple Choice

Most fossils form in ___________ rock.

• igneous

• sedimentary

• metamorphic

​Relative Dating

Does not give an exact date - Age is based on position. The lower down in Earth the older the fossil and time period

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​General markers that help with time estimation - Layer of asteroid dust helps marks 65 Million years ago. Fossils below that line older than 65 million years and fossils above that line are younger than 65 million years

Law of Superposition

This principle states that layers of rock are superimposed, or laid down one on top of another. The oldest rock strata will be on the bottom and the youngest at the top.

Multiple Choice

Where can the oldest layer of fossils be found?

• All the same age

• Top

• Middle

• Bottom

​Index Fossils

​Short-lived species found throughout the world helpful in relative dating

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​ Ammonite index Fossils Trilobite Index Fossil

Mesozoic Era ~ 65 MYA Cambria Period~540 MYA

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​If something was buried near a Fidget Spinner you could estimate age 2017-2019

​If something was buried by a Floppy Disk you could estimate age 1980-late 90's

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Multiple Select

What are requirements for an index fossil to be useful at finding the relative age of rock layers?

• Existed for a short period of geologic time

• Found in many places

• Abundant and plentiful

• Easily recognizable

Multiple Choice

What type of dating indicates an approximate age of a fossil in relationship to other layers of rock in an area?

• relative dating

• absolute Dating

• radiometric dating

• Carbon-14 dating

​Radiometric Dating

​Unstable elements decay or release particles at a predictable rate over time

These unstable elements will decay into stable elements giving a ratio

Unstable Carbon-14 will decay into Stable Nitrogen-14 at a predictable rate

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​Radiometric Dating

​Half-Live - Unit a time it takes an unstable element to decay in half

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Unstable C14 atoms will release a beta particle from the nucleus making in N14

​The billions and billions of C14 atoms in that 10 grams slowly decays into N14

​After 5730 years the 10 grams of C14 decay into 5g N14 and 5g of C14 remain

​After another 5730 years the 5g of C14 decays in 2.5g N14 and 2.5g C14 remain

​Readiometric Dating

​Carbon 14 dating is limitted to fairly recent fossils and is not able to date fossils that are millions of years old.

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​Uranium-235 will decay into Lead-207 with a half live of 704 million years

​Rubidium-87 will decay into Strontium-87 with a half live of 49 billion years

​Potassium-40 will decay into Argon-40 with a half live of 1.25 billion years

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​If you are driving across the US with an average speed of 65 MPH I can determine when you left New York and I can predict when you will roughly be in Iowa and when you will finish the trip without being there in the past when you started or being there in the future when you arrive at the Pacific Ocean.

Multiple Choice

The loss of 50% of a radioactive substance over a certain period of time

• J-Curve

• Half-Life

• Rule of Halves

• Wave Length

Multiple Choice

The fossil record shows that life on Earth ___________________.

• changed over time

• stayed the same

Multiple Choice

What do scientists use to figure out the approximate age of a rock?

• Soil Type

• Plate Tectonics

• Index Fossils

• Genetics

Multiple Choice

In layers of sedimentary rock, the _________ layer is usually at the bottom. Each higher layer is _________ than the layers below it.

• oldest, younger

• youngest, younger

• youngest, older

• oldest, older

Multiple Choice

Method by which a geologist can calculate the absolute age of the rock by knowing the half-life of an isotope.

• Index Fossil Dating

• Absolute Dating

• Radiometric Dating

• Relative Dating

Multiple Choice

Index fossils rely on radioactive isotope.

• yes

• no

Multiple Choice

In which kind of rock do we usually find a fossil?

• Metamorphic

• Volcanic

• Igneous

• Sedimentary

Multiple Choice

The disappearance of a species.

• Evolution
• Extinction
• Migration
• Mutation

Multiple Choice

Method by which order of events or age of rocks is determined by examining the position of rocks in a layer

• Index Fossil Dating

• Absolute Dating

• Radiometric Dating

• Relative Dating

Multiple Choice

An organism is ______________ if it no longer exits and will never live again on Earth.

• rare

• plentiful

• extinct

• radioactive

Multiple Choice

Remains, imprints or traces of once-living organisms

• Detritus

• Fossil

• Pollution

• Fuel

Multiple Choice

If scientists found a ocean fish fossil under your feet what could they infer?

• Fish can breathe oxygen in the past

• The area you are in was once under the ocean

• What ocean fish look like today

• What ate ocean fish ate in the past.