Download Land Form Master with Definitions Mesa

Land Form Master with Definitions
Mesa - Mesas are formed by erosion, when water washes smaller and softer
types of rocks away from the top of a hill. The strong, durable rock that
remains on top of a mesa is called caprock. A mesa is usually wider than it is
tall. Mesas are usually found in dry regions where rock layers are horizontal.
Butte - Buttes form by weathering and erosion when hard caprock overlies a
layer of less resistant rock that is eventually worn away. The harder rock on
top of the butte resists erosion. The caprock provides protection for the
less resistant rock below from wind abrasion which leaves it standing
isolated.
Canyon - The movement of rivers, the processes of weathering and erosion,
and tectonic activity create canyons. The most familiar type of canyon is
probably the river canyon. The water pressure of a river can cut deep into a
river bed. Sediments from the river bed are carried downstream, creating a
deep, narrow
Caves - Caves are formed by the dissolution of limestone. Rainwater picks up
carbon dioxide from the air and as it percolates through the soil, which
turns into a weak acid. This slowly dissolves out the limestone along the
joints, bedding planes and fractures, some of which become enlarged enough
to form caves.
Valley - A valley formed by flowing water, or river valley, is usually V-shaped.
The exact shape will depend on the characteristics of the stream flowing
through it. Rivers with steep gradients, as in mountain ranges, produce steep
walls and a bottom.
G. Hall 4/2017
Cliff - Cliffs are common on coasts, in mountainous areas, escarpments and
along rivers. Cliffs are usually formed by rock that is resistant to
weathering and erosion. Sedimentary rocks most likely to form cliffs include
sandstone, limestone, chalk, and dolomite. Igneous rocks such as granite and
basalt also often form cliffs.
Arches - Weather-eroded arches begin their formation as deep cracks
which penetrate into a sandstone layer. Erosion occurring within the cracks
wears away exposed rock layers and enlarges the surface cracks isolating
narrow sandstone walls which are called fins.
Lakes - All lakes fill bowl-shaped depressions in the Earth's surface, called
basins. Lake basins are formed in several ways. Many lakes, especially those
in the Northern Hemisphere, were formed by glaciers that covered large
areas of land during the most recent ice age, about 18,000 years ago.
Mountains - Movements of tectonic plates create volcanoes along the plate
boundaries, which erupt and form mountains. A volcanic arc system is a
series of volcanoes that form near a subduction zone where the crust of a
sinking oceanic plate melts.
Delta - When a river reaches a lake or the sea the water slows down and
loses the power to carry sediment. The sediment is dropped at the mouth of
the river. Some rivers drop so much sediment that waves and tides can't
carry it all away. It builds up in layers forming a delta.
G. Hall 4/2017