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A watering hole is a natural depression where water collects and animals come to drink. Karst closed depression with permanent lake Stymfalia, Peloponnese, Greece. Seasonal abundant precipitation drained by 3 sinkholes. In geology, a depression is a landform sunken or depressed below the surrounding area. Depressions form by various mechanisms.
Cuesta – Hill or ridge with a gentle slope on one side and a steep slope on the other; Dissected plateau – Plateaus area that has been severely eroded so that the relief is sharp; Erg – Broad area of desert covered with wind-swept sand; Etchplain – Plain where the bedrock has been subject to considerable subsurface weathering
Isostatic depression is the sinking of large parts of the Earth's crust into the asthenosphere caused by a heavy weight placed on the Earth's surface, often glacial ice during continental glaciation. [2] Isostatic depression and isostatic rebound occur at rates of centimeters per year. Greenland is an example of an isostatically depressed region.
One of the world's best-preserved mineralized calderas is the Sturgeon Lake Caldera in northwestern Ontario, Canada, which formed during the Neoarchean era [14] about 2.7 billion years ago. [15] In the San Juan volcanic field , ore veins were emplaced in fractures associated with several calderas, with the greatest mineralization taking place ...
A unit of area traditionally defined as the area of a plot of land one chain (66 feet) by one furlong (660 feet), equivalent to 43,560 square feet (0.001563 sq mi; 4,047 m 2), or about 0.40 hectare. active volcano A volcano that is currently erupting, or one that has erupted within the last 10,000 years (the Holocene) or during recorded history ...
The Hollow Earth is an obsolete concept proposing that the planet Earth is entirely hollow or contains a substantial interior space. Notably suggested by Edmond Halley in the late 17th century, the notion was disproven, first tentatively by Pierre Bouguer in 1740, then definitively by Charles Hutton in his Schiehallion experiment around 1774.
An impact crater is a depression in the surface of a solid astronomical body formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, [2] impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. [3]
In Burroughs' concept, the Earth is a hollow shell with Pellucidar as the internal surface of its shell. Pellucidar is accessible to the surface world via a polar tunnel, allowing passage between both the inner and outer worlds [3] through which a rigid airship visits in the fourth book of the series. [4]