Earth's Geologic History Unit Final

Which layer is the oldest in a sequence of undisturbed rock layers?

• The topmost layer

• The middle layer

• The bottommost layer

• All layers are the same age

Answer explanation

In a sequence of undisturbed rock layers, the bottommost layer is the oldest. This is due to the principle of superposition, which states that in undisturbed layers, older rocks are found beneath younger ones.

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NGSS.MS-ESS1-4

Which type of dating method is used to determine the which rock layers are older or younger, even if you don't know exactly how old each layer is?

• Radiometric dating

• Carbon dating

• Relative dating

• Absolute dating

Answer explanation

Relative dating is used to determine the age of rock layers in relation to one another, identifying which layers are older or younger without needing to know their exact ages.

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NGSS.MS-ESS1-4

In a sequence of rock layers, which layer would contain the youngest fossils?

• The topmost layer

• The middle layer

• The bottommost layer

• All layers contain fossils of the same age

Answer explanation

In a sequence of rock layers, the principle of superposition states that the topmost layer is the youngest. Therefore, the topmost layer would contain the youngest fossils.

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NGSS.MS-ESS1-4

A dinosaur bone is found in layer C, and a seashell is found in layer A. Which is older?

• The dinosaur bone

• The seashell

• They are the same age

• Cannot be determined

Answer explanation

The dinosaur bone is found in layer C, which is typically younger than layer A where the seashell is found. Therefore, the dinosaur bone is older than the seashell.

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NGSS.MS-ESS1-4

If a volcanic eruption covers existing rock layers with ash, where would the ash layer be in relation to the existing layers?

• Below all existing layers

• Above all existing layers

• Between the oldest and youngest layers

• Mixed within the existing layers

Answer explanation

The ash layer from a volcanic eruption is deposited on top of existing rock layers, making it the most recent layer. Therefore, it is located above all existing layers.

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NGSS.MS-ESS1-4

What does the presence of seashell fossils high up on a mountain suggest about the area's past?

• The land that formed the mountain was once underwater

• Seashells can grow on mountains

• The mountain was formed by volcanic activity

• The area was always a mountain

Answer explanation

The presence of seashell fossils high on a mountain indicates that the area was once underwater, as seashells are marine organisms. This suggests significant geological changes that raised the land to its current elevation.

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NGSS.MS-ESS1-4

How can the principle of superposition help determine the relative ages of fossils found in different rock layers?

• By measuring the thickness of each layer

• By identifying the types of fossils in each layer

• By stating that older layers are found below younger layers

• By using radiometric dating techniques

Answer explanation

The principle of superposition states that in undisturbed rock layers, older layers are found below younger layers. This helps determine the relative ages of fossils by their position in the layers.

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NGSS.MS-ESS1-4

Scientists find no more mammoth fossils in younger rock layers, but they do find mammoth fossils in older layers. What might this indicate?

• Mammoths evolved into a different species

• Mammoths migrated to another area

• Mammoths became extinct over time

• Mammoths were never present in the area

Answer explanation

The presence of mammoth fossils only in older rock layers suggests that they existed in the past but are no longer found in younger layers, indicating that mammoths became extinct over time.

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Arrange the following events in Earth's history from oldest to youngest: Dinosaurs roam the Earth, First fish appear, First humans appear, First plants grow on land.

• First humans appear, Dinosaurs roam the Earth, First fish appear, First plants grow on land

• First fish appear, First plants grow on land, Dinosaurs roam the Earth, First humans appear

• Dinosaurs roam the Earth, First fish appear, First plants grow on land, First humans appear

• First plants grow on land, First fish appear, First humans appear, Dinosaurs roam the Earth

Answer explanation

The correct order is: First fish appear (around 500 million years ago), First plants grow on land (about 470 million years ago), Dinosaurs roam the Earth (approximately 230 million years ago), and First humans appear (around 2 million years ago).

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NGSS.MS-ESS1-4

Which extinction was MOST LIKELY caused by a meteor impact, based on the evidence?

• The extinction of species A

• The extinction of species B

• The extinction of species C

• The extinction of species D

Answer explanation

The extinction of species C is most likely linked to a meteor impact due to evidence of iridium in the FIRST LAYER WHERE C IS NO LONGER PRESENT. We know that species have gone extinct when we no longer find fossils in the rock layers. The first rock layer without fossils can give clues as to what CHANGED that might have led to the extinction of that species. Watch the video (you can scroll to minute 2:35 OR watch the whole thing--it's cool!).

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NGSS.MS-ESS1-4