History of the Earth

Which of the following is true about unconformities?

• They are hollow gaps in the rock.

• They represent a gap in time.

• They are always a few hundred years old.

• They are older than the rock layers.

Fill in the blank: Geologists use clues from rock layers to build a record of Earth's ________.

• history

• future

• weather

• population

Index fossils are used to determine the relative ages of rock formations by:

• providing absolute ages for the rocks

• indicating the environment of deposition

• matching rocks of the same age across different regions

• showing the exact sequence of events

How have scientists been able to determine the absolute ages of rocks?

• Radiometric dating

• Astrology

• Dowsing

• Alchemy

What is an index fossil?

• A fossil found only in one specific location

• A fossil used to estimate the absolute age of rock layers

• A fossil that existed for a short period of time and is found in multiple locations

• A fossil that is always found in older rock layers.

The oldest rocks are found at the top of the rock formation. True or False.

• True

• False

Geologists use correlation to fill in gaps in the rock record by matching fossils from different locations.

• True

• False

Absolute age refers to the age of rocks compared to other nearby rocks.

• True

• False

Index fossils are important for correlating rock layers across different locations because they:

• are found in only one location

• are found in multiple locations and represent a specific time period

• are the oldest fossils found

• are the most abundant fossils

The discovery of radioactivity was significant for determining the absolute age of rocks because it allowed for:

• the measurement of radioactive decay rates

• the identification of rock types

• the estimation of rock density

• the analysis of rock color