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Rock Layers and Fossil Evidence
Earth has many rock layers. These are the layers of natural material that pile up over time. These materials eventually turn to rock. Rock layers show how Earth has changed. Scientists study patterns in these layers. They can identify plants and animals that lived at different times. These patterns also show natural forces that acted on landforms in the past.

Rock Layers
Observing rock layers proves that the landscape of Earth has changed. Over time, small particles of rock break down. This process continuously repeats until enough particles have accumulated. They bury the older material. The material beneath the sediment eventually turns to rock.


Rock layers are the result of small particles of rock breaking down and accumulating over time.
Plant and animal remains are buried over time. Sediment piles on top of them. They are put under a great deal of pressure. After millions of years, these remains turn into fossils. Fossils are any traces of animals or plants preserved within rock.

Rock layers reveal the order in which Earth has changed. The lower layers were formed first. They were covered over time by the layers above them. An area changed in order from the lowest layer to the highest layer. The deeper we dig into these rock layers, the farther back in time we can see.


The deeper under Earth’s surface a rock layer is, the longer ago it is from.
Fossil Patterns
Rock layers can reveal fossil patterns. These show what lived during different times in history. Scientists study these fossil patterns. They can identify relationships between living things that are now extinct. Fossils show the different plants and animals that lived in the past.


Fossils within rock layers show the different plants and animals that lived at different points in time.
Scientists also study the order of fossils within rock layers. This helps them understand the natural history of an area. For example, there may be marine fossils at the lower layers. This would mean that the area was once underwater. Upper levels may have fossils of land animals. These patterns can show when this area of land became dry.

Irregular Patterns
Rock layers often form in a clear order. However, the layers can be disrupted. This causes irregularities in the rock layers. These irregularities show evidence of natural forces. For example, imagine a canyon with a river flowing at the bottom. The canyon walls reveal different rock layers. This shows that over time, the river cut through the rock to form the canyon.


This photograph shows the Grand Canyon, which was formed over the course of millions of years by the Colorado River flowing through it.
Irregularities also occur along fault lines. These are cracks in rock formed by plates moving beneath the earth’s surface. This causes the rock to slide out of place. This disrupts the layers. Shifting plates are often responsible for earthquakes and volcanoes. Scientists can study rock layers to find evidence of these events.

Rock layers tell the natural history of our planet. They show how Earth has changed over millions of years. They allow us to see the unique plants and animals that once lived. These layers serve as a history book. They give us a glimpse of how the earth looked long ago.

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Questions
How are fossils and rock layers related?

Fossils help scientists understand why a rock layer looks the way it does.

Fossils found in rock layers can help scientists learn about life in an area at a certain time in history.

Rock layers are found below fossil layers.

Fossils have nothing to do with rock layers.
Which of the following words are synonyms for the word “irregular”? Select two.

Not normal

Not regular

Similar

Far away
What happens when something accumulates?

A rock pile breaks up

Things fly away

A bunch of things gather or pile up

Older things break down
According to the text, which of the following ideas are things you can determine from rock layers?

What the landscape of Earth was at a certain time

What kinds of plants and animals lived in an area at a certain time

What the landscape will look like in the future

When a certain natural disaster will happen
Please answer all questions

Answer 1

1) Fossils found in rock layers can help scientists learn about life in an area at a certain time in history.

2) Not normal; Not regular.

3) A bunch of things gather or pile up.

4) What the landscape of Earth was at a certain time; What kinds of plants and animals lived in an area at a certain time.