Both climates are dominated by heavy denudation. Box Box valleys have wide, relatively level floors and steep sides. They are common in periglacial areas and occur in mid-latitudes, but also occur in tropical and arid regions. Rift Rift valleys, such as the Albertine Rift and Gregory Rift are formed by the expansion of the Earth's crust due to tectonic activity beneath the Earth's surface. Terms for valleys There are many terms used for different sorts of valleys. They include: Cove: A small valley, closed at one or both ends, in the central or southern Appalachian Mountains which sometimes results from the erosion of a geologic window. Dell: A small, secluded, and often wooded valley. Dry valley: A valley not created by sustained surface water flow. Erosional Valley: A valley formed by erosion. Hollow: A term used regionally for a small valley surrounded by mountains or ridges. In Ireland, New England, Appalachia, and the Ozarks of Arkansas and Missouri, a hollow is a small valley or dry stream bed. Longitudinal valley: An elongated valley found between two nearly-parallel mountain chains. Steephead Valley: A deep, narrow, flat-bottomed valley with an abrupt ending. Strike Valley: A valley typically developed parallel to a cuesta from more readily eroded strata. Structural Valley: A valley formed by geologic events such as drop faults or the rise of highlands. Similar geographical features such as gullies, chines, and kloofs, are not usually referred to as valleys. British regional terms for valleys The terms corrie, glen, and strath are all Anglicisations of Gaelic terms and are commonly encountered in place-names in Scotland and other areas where Gaelic was once widespread. Strath signifies a wide valley between hills, the floor of which is either level or slopes gently. A glen is a river valley which is steeper and narrower than a strath. A corrie is a basin-shaped hollow in a mountain. Each of these terms also occurs in parts of the world formerly colonized by Britain. Corrie is used more widely by geographers as a synonym for (glacial) cirque, as is the word cwm borrowed from Welsh. The word dale occurs widely in place names in the north of England and, to a lesser extent, in southern Scotland. As a generic name for a type of valley, the term typically refers to a wide valley, though there are many much smaller stream valleys within the Yorkshire Dales which are named