Earth’s Landscapes

Before Video

• A fossil is evidence of past life on Earth.

• 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.

• 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.

• 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

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

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.