Science Olympiad Dynamic Planet Practice Test

What geological evidence supports the existence of a Snowball Earth?

1. Presence of igneous intrusions

2. Location of fossilized coral reefs

3. Presence of glacial deposits

4. Formation of oceanic ridges

The correct answer is: Presence of glacial deposits

The presence of glacial deposits is key evidence supporting the concept of Snowball Earth, which refers to periods in Earth's history when the planet's surface was entirely or nearly entirely frozen. During these glaciation events, glacial deposits, also known as till, were laid down by moving ice sheets. The identification of such deposits, particularly in regions that are now located near the equator, indicates that these areas experienced significant glaciation during those historical periods. These deposits are often characterized by their distinctive characteristics, such as unsorted mixtures of sediment and large boulders (glacial erratics), which provide a clear indication of past ice movement and the extent of glaciation. The recognition of similar deposits across diverse geographic regions suggests that the Earth's climate was drastically altered, supporting the hypothesis that the entire planet could have been covered in ice at times. Other options do not provide the same direct evidence for Snowball Earth. For instance, igneous intrusions and the formation of oceanic ridges pertain more to volcanic activity and tectonics rather than glacial history. Fossilized coral reefs typically indicate warmer marine environments, contradicting the conditions expected during a Snowball Earth scenario. Thus, glacial deposits serve as the most compelling geological