earth unit fossils and geological history power point
DESCRIPTION
6th grade science unit on Planet Earth- focus on how fossils and rock layers help scientists learn about the history of the EarthTRANSCRIPT
How do fossils and rock layers tell time?
Geological History
What are fossils?
A remnant or trace of an organism of a past geologic age, such as a skeleton or leaf imprint, embedded and preserved in the earth's crust. (www.answers.com)
There are different kinds of fossils, including molds, casts, trace, and true form fossils.
Fossils
How are rocks and fossils use to understand the age and history of
the Earth?
Some kinds of animals and plants lived only for a short time before becoming extinct. Their fossil remains are found in rocks.
For example, one type of coral lived 50 million years ago and then died out. Its fossils are found only in rock that formed 50 million years ago. Rocks that formed earlier or later do not contain this fossil.
Scientists use this coral fossil as an index fossil. It can help them determine the age of rocks they uncover. When scientists find this type of fossil, they know that the rock is about 50 million years old.
For other time periods in Earth’s past, scientists use other index fossils.
Hall, Carol. Earth & Space Science. 1999.
How are rocks and fossils use to understand the age and history of
the Earth?
As sediment collects at the bottom of bodies of water, the remains of dead plants and animals are deposited within the sediment.
This creates a record of the life around at the time the sediments were deposited.
The oldest, or first, life is found in the deepest layer of sediment.
Oldest layer
Newest layer
Fossil
How are rock layers exposed?
Rock layers can become exposed in a variety of ways, including: Weathering Erosion Mountains forming Building roads Scientific work
Conclusion:What are the key concepts I learned today?
•Index fossils help scientists tell when rock layers formed.•Fossils and rock layers provide important evidence of how life and environmental conditions have changed.•Fossils and rock layers provide evidence about the plants and animals that lived long ago and the nature of the environment at that time.•Rocks form in layers over time. The oldest rock layers is at the bottom while the younger layers form on top of it.
