Transcript LANDFORMS by jn

LANDFORMS
Organized and edited by
Joe Naumann
UMSL
Four Major Categories
• Mountains
• Hills
• Plateaus
• Plains
Mountains
Hills
Plain
Formation of Landforms
• Endogenous forces
– Resulting from dynamic processes
operating beneath the crust of the Earth.
• Diastrophism: Lifting of a large part of the
crust in elevation
• Orogeny: Folding, warping, faulting in the
crust which may occur as a result of
diastrophism.
• Volcanism: a process whereby molten rock
material from beneath the crust pushes
through the crust and builds up the surface of
the earth.
Formation of Landforms
• Endogenous forces
– Landforms (often plains or minor landforms) created
from forces outside the earth which act upon the
surface and change it.
• Weathering: the breaking down of rock by
chemical and/or mechanical means into smaller
particles in preparation for the next two forces.
• Erosion: the removal of weathered materials from
higher elevations by moving water, wind, moving
ice, and/or gravity.
• Deposition: the build up of weathered materials at
lower elevations once the force of gravity cannot be
overcome by an agent of erosion.
Major Landforms
Defined
And illustrated
Mountain
• landform that rises prominently above its
surroundings, generally exhibiting steep
slopes, a relatively confined summit area,
and considerable local relief. Mountains
generally are understood to be larger than
hills, but the term has no standardized
geological meaning. Very rarely do
mountains occur individually. In most cases,
they are found in elongated ranges or
chains.
Hill
• a usually rounded natural elevation of land
lower than a mountain – lower in altitude
and having less local relief. It has very little
level land surface; however, it is usually
much less steep than a mountain.
Hills in the foreground
Plateau
• a usually extensive land area having a
relatively level surface raised sharply above
adjacent land on at least one side
sometimes referred to as a tableland. The
steep surface where it rises sharply above
the adjacent land is called an escarpment.
Plateau in the background
Plain in the foreground
Plateau surface above & the
escarpment
Escarpment
Plain
• any relatively level area of the Earth's
surface exhibiting gentle slopes and small
local relief. Plains vary widely in size. The
smallest occupy only a few hectares,
whereas the largest cover hundreds of
thousands of square kilometers.
• The majority of the world's most extensive
plains were formed as a result of the
dominance of erosional and depositional
processes over tectonic activity—e.g., uplift
or subsidence of the Earth's crust.
Plain in the foreground
Floodplain
The Rock Cycle
How Earth materials are formed,
altered, destroyed and
regenerated
Key points about the rock
cycle
• Diastrophism and orogeny result from the
forces involved in plate tectonics.
• These endogenous forces are largely
responsible for the creation of mountains, hills,
and plateaus.
• Once the endogenous forces transform (uplift)
the earth’s surface, then exogenous forces
begin to further alter the surface.
Rock cycle continued . . .
• Weathering begins breaking down rock material
into smaller, more easily transported pieces.
• Gravity plus moving water, air, and ice remove
weathered particles from the higher elevations.
• When conditions are such that the power of
gravity can overcome the carrying power of
moving water, air, or ice, the weathered
material settles to the surface at a lower
elevation.
• The high places are reshaped and lowered, and
the lower places are filled in, reshaped & raised.
Some minor landforms
created by exogenous
forces.
For a more complete treatment of all
landform types, consult a geology or
earth science textbook.
Karst topography
• Karst topography is a three-dimensional
landscape shaped by the dissolution of a
soluble layer or layers of bedrock, usually
carbonate rock such as limestone or dolomite.
These landscapes display distinctive surface
features and underground drainages, and in
some examples there may be little or no
surface drainage. Some areas of karst
topography, such as southern Missouri and
northern Arkansas in the USA, are underlain by
thousands of caves.
Karst surface features
• The karstification of a landscape may result in a
variety of large or small scale features both on
the surface and beneath. On exposed surfaces,
small features may include flutes, runnels,
clients and grikes, collectively called karren or
lapiez. Medium-sized surface features may
include sinkholes or dolines (closed basins),
vertical shafts, disappearing streams, and
reappearing springs.