Video Lesson: Index Fossils

What is the primary purpose of an index fossil?

• To determine the absolute age of the Earth.

• To identify the type of rock in a sedimentary layer.

• To help determine the age of other fossils and rock in the same sedimentary layer.

• To predict future geological events.

Before the development of radiometric dating, what method did geologists primarily use to determine the relative ages of rock layers and fossils?

• Analyzing the chemical composition of rocks.

• Observing the color variations in rock strata.

• Relative dating based on rock layers and their contained fossils.

• Measuring the magnetic properties of the Earth's crust.

According to the Law of Superposition, what can be inferred about the age of rock layers in a sequence of rock strata?

• Younger layers are always found beneath older layers.

• Older layers are found at the bottom, and younger layers are at the top.

• All rock layers in a sequence are approximately the same age.

• The age of rock layers cannot be determined without radiometric dating.

Which individual is credited with developing the Law of Faunal Succession, which states that older fossils are found in deeper layers and newer fossils are deposited on top?

• Nicholas Steno

• Marie Curie

• William "Strata" Smith

• Ernest Rutherford

If you find a specific type of ammonite fossil in a layer in one location and the same type of fossil in the same layer in another location, what can you conclude about their ages?

• The fossils are from different geological periods.

• The fossils are approximately the same age.

• The fossils are unrelated in age.

• The fossils indicate a major geological upheaval.

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Which of the following is NOT a characteristic of a good index fossil?

• Must be distinctive and easily recognizable.

• Must be globally widespread.

• Must be abundant.

• Must have lived for a very long geological period.

Why are many index fossils derived from marine animals?

• Marine animals are generally larger and easier to fossilize.

• Ocean environments provide better conditions for preservation and widespread dispersal of eggs/larvae.

• Land animals rarely produce fossils.

• Marine fossils are more resistant to erosion.

How can marine index fossils, such as trilobites that lived 500 million years ago, be found on top of mountains like Mount Everest?

• They were carried there by ancient floods.

• The animals migrated to high altitudes before fossilizing.

• Plate tectonics caused ancient oceanic crust, containing these fossils, to be uplifted.

• Wind erosion transported the fossils from the ocean floor to the mountains.