Lesson 2: Comparing Landforms

Key Idea

Geologic events, such as a volcanic eruption or a flowing river, are active geologic processes. When these processes stop, they leave behind physical structures called landforms. A triangular pile of sediment or a curved channel serves as a permanent record of past activity.

On rocky planets like Earth and Mars, specific processes create specific landform shapes. Scientists study these shapes to identify the process that formed them. For instance, flowing water creates distinctive curves that differ from the straight cracks created by tectonic shifts, allowing the landform itself to serve as evidence.

Key Idea

Because humans cannot easily travel to Mars, scientists use a method called comparative planetology. This involves strictly comparing the surface features of an unknown world (Mars) to the well-understood features of a known world (Earth).

When a Martian landform exhibits a similarity in shape and structure to an Earth landform, scientists can infer a shared history. This comparison is a powerful tool. It allows scientists to build a strong argument that the same geologic processes active on Earth today were once active on Mars in the distant past.