Ogives (glaciers)
Encyclopedia
An ogive is a geographic feature of certain types of glaciers. They are identified as light and dark bands of ridges and valleys found at the base of glacial icefall
s. They are usually found on 'advancing' or 'neutral' glaciers.
Ogives are created by icefalls. The icefalls produce a pattern of alternating ridges and swales that gradually flatten out downglacier. They also bend throughout the glacier, because the velocity
of the glacier is greater near the center.
As ice
passes through an icefall it is usually very broken-up, which greatly increases the ablation
surface area in the summer
, and provides space for enhanced entrapment of snowfall during the winter
. Winter ice that passes through the icefall becomes bulgy, irregular and hummocky at the base of the icefall, while summer ice turns into a swale.
Icefall
An icefall is a portion of some glaciers characterized by rapid flow and a chaotic crevassed surface. Perhaps the most conspicuous consequence of glacier flow, icefalls occur where the glacier bed steepens and/or narrows...
s. They are usually found on 'advancing' or 'neutral' glaciers.
Ogives are created by icefalls. The icefalls produce a pattern of alternating ridges and swales that gradually flatten out downglacier. They also bend throughout the glacier, because the velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
of the glacier is greater near the center.
As ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
passes through an icefall it is usually very broken-up, which greatly increases the ablation
Ablation
Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...
surface area in the summer
Summer
Summer is the warmest of the four temperate seasons, between spring and autumn. At the summer solstice, the days are longest and the nights are shortest, with day-length decreasing as the season progresses after the solstice...
, and provides space for enhanced entrapment of snowfall during the winter
Winter
Winter is the coldest season of the year in temperate climates, between autumn and spring. At the winter solstice, the days are shortest and the nights are longest, with days lengthening as the season progresses after the solstice.-Meteorology:...
. Winter ice that passes through the icefall becomes bulgy, irregular and hummocky at the base of the icefall, while summer ice turns into a swale.