The Paleozoic Era (~541-252 million years ago) was a period of dramatic change at the surface of the Earth, starting with a rapid diversification of animals in the oceans, continuing through the colonization of land, and ending with the largest known mass extinction in Earth’s history.
Bedforms are wave-like patterns that develop when a fluid flows over a granular bed. They exist in both fluvial and eolian environments, under the form of, e.g., ripples and dunes.
Amphitheater-shaped canyons on Earth and Mars have horseshoe-shaped heads, steep sidewalls, and roughly uniform widths over their entire length. On Earth, they may form in loose sediment from groundwater seepage erosion, or in more competent lithologies by waterfall erosion during overland flow.
As light from an emitting source, e.g., the Sun, is reflected by a geologic surface, its spectrum becomes the carrier of useful geologic information.