Fossil Vocabulary
What do we call preserved remains of living things?
Fossils
Most fossils are found in what type of rock?
Sedimentary rock
Scientists who study fossils are called ______.
Paleontologists
What is radioactive decay?
When elements release energy as they break down over time
What does extinct mean?
An organism no longer exists and will never live again
A hollow space in rock shaped like an organism is called a ______.
Mold
According to the Law of Superposition, which rock layer is oldest?
The bottom (deepest) layer
Scientists who study rocks are called ______.
Geologists
The time it takes for half of an element to decay is called its ______.
Half-life
What causes rock layers to change?
Erosion and folding
A solid copy of an organism’s shape is called a ______.
Cast
A break in Earth’s crust is called a ______.
Fault
A fossil that helps determine the age of rock layers is called an ______ fossil.
Index fossil
Radioactive elements are usually found in what type of rock?
Igneous rock
What forms when magma reaches Earth’s surface and hardens?
Extrusion (lava)
This fossil forms when minerals replace some or all of the organism.
Petrified fossil
A gap in the geologic record caused by erosion is called an ______.
Unconformity
What are the two ways scientists show a rock’s age?
Relative age and absolute age
What happens to radioactive material during radioactive dating?
Radioactive material decreases and new material increases
Why can’t scientists use carbon dating on most rocks?
Most rocks do not contain carbon
Fossils that show evidence of activities like footprints or burrows are called ______ fossils.
Trace fossils
When forces inside Earth bend rock layers, this process is called ______.
Folding
Why are rock layers important?
They form a record of Earth’s history
Why is Potassium-Argon dating useful for ancient rocks?
Because it has a long (high) half-life
Why can’t carbon-14 be used on organisms older than 50,000 years?
There is too little carbon-14 left