Geologic Time Scale

Scientists use radioactive dating techniques to estimate

• the lifespan of an Earth material.

• the age of the sun and the solar system.

• the age of an Earth material.

• the time it takes for a rock to change into soil.

In what time did Pangaea, the supercontinent, appear?

• Mesozoic Era

• Cenozoic Era

• Paleozoic Era

• Precambrian Time

Scientists found a fossil of a horse, fossil X, in a shallow rock layer. In a much deeper rock layer, they found fossil Y, which was a fossil from an animal that closely resembled a horse but was the size of a dog. Based on this explanation, what is the best explanation for these findings?

• Fossil Y is older so over time it dried out and became smaller than fossil X.

• The animal that formed fossil Y has no relationship to the animal that formed fossil X.

• Fossil Y is smaller because it formed from a younger animal than fossil X.

• The animal that formed fossil y is a distant relative of fossil X.

Mason and Clara are geologists who are digging for fossils. As they locate fossils, they map the location of them to help other geologists understand Earth's history and how life on Earth has changed over time. Mason locates a gastropod and makes the claim, "Gastropods are index fossils." Clara disagrees with Mason. Which of the following best supports Clara's disagreement?

• To be classified as an index fossil, the fossil must be unique. Since the gastropod is not unique, it cannot be an index fossil.

• An index fossil must be found over a wide area of the Earth. Since the gastropod is widely spread, it cannot be an index fossil.

• To be an index fossil, the fossil of the organism must be found in many rock layers. Since the gastropod is not found in every layer, it cannot be an index fossil.

• If a fossil is to be considered an index fossil, the organism must have lived only a short period of time. Since the gastropod lived a long period of time it is not an index fossil.

This diagram shows the location of a mammoth fossil found in rock layers at an excavation site. The mammoth that formed the fossil lived during the Ice Age. These types of data have helped scientists to determine that triceratops dinosaurs became extinct before mammoths live. What other evidence have scientists most likely found that helped them determine that mammoths lived after triceratops became extinct?

• More triceratops fossils have been found than mammoth fossils.

• Fossils of triceratops have been found only in rock layers that are deeper than mammoth fossils.

• Fossils of triceratops have been found only in rock layers that are above layers where mammoth fossils have been found.

• More mammoth fossils have been found than triceratops fossils.

Analysis of rock strata and the fossil record provide

• a revolving scale.

• relative dates.

• absolute dates.

• an absolute scale.

In which time period are we currently living?

• Cenozoic Era

• Precambrian Time

• Mesozoic Era

• Paleozoic Era

Dinosaurs, small mammals, and birds appeared in this time period.

• Cenozoic Era

• Precambrian Time

• Mesozoic Era

• Paleozoic Era

Which time period is the longest?

• Mesozoic Era

• Cenozoic Era

• Paleozoic Era

• Precambrian Time

Jellyfish are one of the oldest species on Earth. In what time period did they first appear?

• Mesozoic Era

• Cenozoic Era

• Precambrian Time

• Paleozoic Era