Earth History

Front

What is the name of the sedimentary rock layer that was the last to form before an unconformity?

Back

The last sedimentary rock layer before an unconformity is referred to as the 'youngest layer' or 'top layer' in geological terms.

Front

Which rock unit is typically the youngest in a geological cross-section?

Back

The youngest rock unit is usually the one that is on top of the other layers, as sedimentary layers are deposited in a chronological order.

Front

What type of rock is sandstone?

Back

Sandstone is a sedimentary rock composed mainly of sand-sized mineral particles or rock fragments.

Front

Why can volcanic ash be used as a time marker in geology?

Back

Volcanic ash can be used as a time marker because it is deposited rapidly over a large area, allowing for correlation between rock layers.

Front

What is an index fossil?

Back

An index fossil is a fossil that is used to define and identify a particular time period in the geological time scale.

Front

Name a common index fossil from the Early Ordovician period.

Back

Climacograptus is a common index fossil from the Early Ordovician period.

Front

What is an unconformity in geology?

Back

An unconformity is a surface of contact between two groups of unconformable strata.

Front

What does the Law of Superposition state?

Back

The Law of Superposition states that in any undisturbed sequence of rocks, the oldest layers are at the bottom and the youngest are at the top.

Front

What is the significance of the rock cycle?

Back

The rock cycle describes the transitions through geologic time among the three main rock types: igneous, sedimentary, and metamorphic.

Front

How does sedimentary rock form?

Back

Sedimentary rock forms through the accumulation and compaction of mineral and organic particles over time.