A fossil is evidence of past life on Earth.

Has the landscape you live in always looked the way it does now?

Most landscapes have changed over time. Looking at rock layers and the fossils they contain can provide evidence and clues about what it was like in the past.

How can shark teeth be found 100 miles away from the ocean?

Fossils from marine life found in what is now land provides evidence that the landscape has changed over time and the land was once under the sea.

Does the Earth change or stay the same over time? How do you know?

The Earth changes over time. Some changes happen quickly, like earthquakes and volcanoes. Other changes are slow — like erosion and plate tectonics. We can see evidence of these changes in rock layers that help us understand the past.

What kinds of evidence supports the idea that the landscape at Sharktooth Hill was once under the ocean?

Fossils from whales, sharks, dolphins, and turtles are found there along with silt, which is sediment found at the bottom of the ocean.

Why is it possible to find ancient fossils right at the Earth’s surface?

Although the layer of rock that contains the fossils found at Sharktooth Hill is very old, it is exposed at the Earth’s surface in some areas of the dig site so fossils can be found right on the ground. Older rocks above this fossil layer eroded over time due to water and/or wind.

Is there any evidence that a volcano caused all the animals to die here?

No. Scientist have not found any volcanic ash in the rock layer. They also ruled out that all the animals were eaten by sharks because very few shark bites have been found on other animals’ bones. There is no evidence to support these theories.

What is the current understanding of how the fossil bone bed at Shark Tooth Hill formed?

The silt the bones are buried in is thought to have come from a river depositing fine sand and clay on the bottom of the ocean. Animals who died naturally in that area would have been buried and fossilized. Scientists think that the river may have stopped flowing for some time (due to a change in the climate), which meant sediment was not being deposited and animal skeletons collected on the sea floor. When the climate shifted and the river started flowing again, sediment then buried all the collected skeletons, forming the bone bed.

How do the rock layers above and below the bone bed compare in age?

The rock layers above the bone bed are younger than the bone bed. The rock layers below the bone bed are older than the bone bed.

Where would you look for evidence of what it was like before the bone bed formed?

To know about the environment before the time the bone bed formed, you would need to dig deeper than the bone bed. Layers below it would be older.

How did the bones in the Sharktooth Hill bone bed become jumbled up?

Scientists think that the bones were jumbled together by ocean currents. They know all the bones are about the same age due to radiocarbon dating.

How do we know the central part of the United States was once covered by the ocean?

Fossils from sea creatures found in what is now the plains of the Midwest provide evidence that this area was once covered by the sea.

Earth’s Landscapes

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Earth’s Landscapes

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What you will learn from this videoWhat you will learn

Rock layers provide evidence of Earth’s landscapes from the past.
The oldest rock layers are at the bottom and the newest layers are at the top.
The location of fossils in rock layers provides evidence of earth’s past landscapes.

Discussion Questions
- Before Video
  What is a fossil?ANSWER
  - A fossil is evidence of past life on Earth.
  Has the landscape you live in always looked the way it does now? ANSWER
  - Most landscapes have changed over time. Looking at rock layers and the fossils they contain can provide evidence and clues about what it was like in the past.
  How can shark teeth be found 100 miles away from the ocean?ANSWER
  - Fossils from marine life found in what is now land provides evidence that the landscape has changed over time and the land was once under the sea.
  Does the Earth change or stay the same over time? How do you know?ANSWER
  - The Earth changes over time. Some changes happen quickly, like earthquakes and volcanoes. Other changes are slow — like erosion and plate tectonics. We can see evidence of these changes in rock layers that help us understand the past.
- After Video
  What kinds of evidence supports the idea that the landscape at Sharktooth Hill was once under the ocean?ANSWER
  - Fossils from whales, sharks, dolphins, and turtles are found there along with silt, which is sediment found at the bottom of the ocean.
  Why is it possible to find ancient fossils right at the Earth’s surface?ANSWER
  - Although the layer of rock that contains the fossils found at Sharktooth Hill is very old, it is exposed at the Earth’s surface in some areas of the dig site so fossils can be found right on the ground. Older rocks above this fossil layer eroded over time due to water and/or wind.
  Is there any evidence that a volcano caused all the animals to die here?ANSWER
  - No. Scientist have not found any volcanic ash in the rock layer. They also ruled out that all the animals were eaten by sharks because very few shark bites have been found on other animals’ bones. There is no evidence to support these theories.
  What is the current understanding of how the fossil bone bed at Shark Tooth Hill formed?ANSWER
  - The silt the bones are buried in is thought to have come from a river depositing fine sand and clay on the bottom of the ocean. Animals who died naturally in that area would have been buried and fossilized. Scientists think that the river may have stopped flowing for some time (due to a change in the climate), which meant sediment was not being deposited and animal skeletons collected on the sea floor. When the climate shifted and the river started flowing again, sediment then buried all the collected skeletons, forming the bone bed.
  How do the rock layers above and below the bone bed compare in age?ANSWER
  - The rock layers above the bone bed are younger than the bone bed. The rock layers below the bone bed are older than the bone bed.
  Where would you look for evidence of what it was like before the bone bed formed?ANSWER
  - To know about the environment before the time the bone bed formed, you would need to dig deeper than the bone bed. Layers below it would be older.
  How did the bones in the Sharktooth Hill bone bed become jumbled up?ANSWER
  - Scientists think that the bones were jumbled together by ocean currents. They know all the bones are about the same age due to radiocarbon dating.
  How do we know the central part of the United States was once covered by the ocean?ANSWER
  - Fossils from sea creatures found in what is now the plains of the Midwest provide evidence that this area was once covered by the sea.
Vocabulary
- Fossil DEFINE
- Sharktooth Hill DEFINE
- Paleontology DEFINE
- Silt DEFINE
- Sedimentary Rock DEFINE
- Bone bed DEFINE
- Rock layer DEFINE
- Radiocarbon dating DEFINE
- Earth’s Landscapes DEFINE
- Grand Canyon DEFINE
- Erosion DEFINE
Reading Material
DIY Activity Guide
Lesson Plan
Lesson Plan
Teacher Guide
Assessment
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