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Also called bidirectional ripples, or symmetrical ripple marks have a symmetrical, almost sinusoidal profile; they indicate an environment with weak currents where water motion is dominated by wave oscillations. In most present-day streams, ripples will not form in sediment larger than coarse sand.
Bi-directional ripples are rarely symmetrical due to the difference in force of the two directions, where as the wave formed or oscillation ripples form from the circular water movement pattern of water molecules. These ripples form parallel to the shore line. They usually display rounded troughs and rounded crests. Wave motion-i18n
Wave ripple or symmetric ripple, from Permian rocks in Nomgon, Mongolia with "decapitation" of ripple crests due to change in current. Ripple marks usually form in conditions with flowing water, in the lower part of the Lower Flow Regime. There are two types of ripple marks: Symmetrical ripple marks
Cross-bedding forms during deposition on the inclined surfaces of bedforms such as ripples and dunes; it indicates that the depositional environment contained a flowing medium (typically water or wind). Examples of these bedforms are ripples, dunes, antidunes, sand waves, hummocks, bars, and delta slopes. [1]
Sand waves are formed through the action of the wind or water (through waves or tidal currents) [2] and are a product of unidirectional flow. Sand waves are the result of a mean flow velocity between 40 and 70 cm/s. Sand waves also form underwater. [3] [4]
Current ripples preserved in sandstone of the Moenkopi Formation, Capitol Reef National Park, Utah, United States. A bedform is a geological feature that develops at the interface of fluid and a moveable bed, the result of bed material being moved by fluid flow. Examples include ripples and dunes on the bed of a river.
Water flow is away from the camera. An antidune is a bedform found in fluvial and other channeled environments. Antidunes occur in supercritical flow , meaning that the Froude number is greater than 1.0 or the flow velocity exceeds the wave velocity; this is also known as upper flow regime .
Ripple marks are small ridges of sediment that form due to wind or water blowing over loose sediment in either a current or wave pattern. Aeolian ripples result from high velocity winds which form fine, well-sorted grain particles into long, flat, asymmetrical ripples. [citation needed]