Ancient currentsThis photo captures remnants of flowing currents over 100 million years ago. These r

Ancient currentsThis photo captures remnants of flowing currents over 100 million years ago. These ripples form exactly as ripples do when currents flow today; moving water causes grains to bounce along the bottom of the flow and eventually they stack upwards into hills that cascade over the top, with troughs in-between.Ripples are distinct enough that scientists can actually measure information about the ancient flow by looking at properties like grain size, size of the ripple, and spacing between each ripple. Those properties can tell us how deep water flows were, how fast they were moving, and which direction the water was flowing. In this case, there are actually two flow directions preserved, as you can see by the interfering pattern of ripples. Interference ripples can form during floods, as waves refract around obstacles that are newly submerged, or in ephemeral (short lived) streams where the flow pattern changes as obstacles are exposed. Preserving a pattern like this one also requires that other sediment rapidly buried the ripples before the current could rework them.These ripples were observed in Dinosaur Ridge, a structure just east of the Rocky Mountain Front Range in Colorado.-JBBImage credit: James St. Johnhttps://flic.kr/p/dByJVJReference:http://jsedres.geoscienceworld.org/content/40/2/708.short -- source link
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