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Learn 10 high-impact geology facts frequently asked in Geology examinations such as GATE, JAM, NET, UPSC Geology Optional…

Terms featured also appear in our Terra Crack #004 learning series.

Barchan Dunes

Barchan dunes are crescent‑shaped sand ridges with their horns pointing downwind. They form where sand supply is limited and winds blow predominantly from one direction. Their smooth, gentle stoss side faces the wind, while the steeper slip face on the lee side migrates downwind as grains avalanche over the crest.

Transverse Dunes

Transverse dunes appear as a series of parallel ridges oriented at right angles to the prevailing wind. They develop in areas with abundant sand and a constant wind direction. Over time, individual dune crests grow and merge, creating broad “corridors” of sand that march slowly across the landscape.

Linear (Seif) Dunes

Linear—or seif—dunes are long, narrow ridges that align roughly parallel to the prevailing wind direction. They form under bidirectional wind regimes that alternately blow from two similar directions. Seif dunes can stretch for tens to hundreds of kilometers, often with sharp crests and symmetrical cross‑sections.

Star Dunes

Star dunes are pyramidal piles of sand with multiple radiating arms or ridges jutting out in several directions. They develop where wind patterns are highly variable, converging from different directions over time. Their complex form grows upward rather than migrating laterally, making them some of the tallest dunes on Earth.

Parabolic Dunes

Parabolic dunes are U‑shaped mounds of sand with their open ends—or horns—pointing upwind. They commonly form in coastal or semi‑arid regions where vegetation partly stabilizes the dune flanks. As the wind erodes the central section, the anchored horns remain in place, creating a distinctive parabolic outline.

Dome Dunes

Dome dunes are small, rounded mounds of sand with no slip face or identifiable crest orientation. They form under light, multidirectional winds and a moderate sand supply. Because they lack a defined leeward side, dome dunes tend to remain relatively fixed in place unless wind regimes change.

Yardangs

Yardangs are streamlined, ridge‑like rock features sculpted by persistent wind erosion. They typically have a blunt upwind end and a tapered tail pointing downwind. Found in arid regions where fine sand grains act like natural sandblasting tools, yardangs can range from a few meters to several kilometers in length.

Ventifacts

Ventifacts are individual rocks whose surfaces have been polished, pitted, or faceted by wind‑driven sand. Each facet corresponds to a prevailing wind direction, and multiple wind regimes can carve several faces on a single stone. These wind‑abraded stones often accumulate in coarse gravel pavements where finer sediments have been blown away.

Blowouts (Deflation Hollows)

Blowouts are shallow, bowl‑shaped depressions formed by the wind’s removal of loose sediment. They usually develop in sand‑covered areas where vegetation is sparse or disturbed. As wind scours out the depression, the displaced sand may be deposited as small dunes or ripples around the blowout’s perimeter.

Loess Deposits

Loess consists of extensive blankets of fine silt and very fine sand deposited by wind, often downwind of glacial or desert regions. These deposits can form thick, fertile soils that support rich agricultural lands. Because loess particles are loosely packed, areas underlain by them are prone to erosion and collapse if the surface is disturbed.

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