Landforms
Physiography and Topography
Landforms
When most people speak of topography, they are actually referring to physiography.
Topography refers to all of the surface features of an area. This includes
the surface elevation, vegetation, roads and buildings, and other features
commonly found on topographic maps. Physiography is only the geologic surface
or terrain features of an area. These are also known as landforms. Among
the more common landforms are mountains, hills, valleys, cliffs, and plains.
The study of landforms is known as geomorphology. Geomorphology is studied
by both geographers and geologists. It is that portion of geology that is
of most interest to geographers because it helps to explain the physical
environment which provides both the settings and opportunities for human
settlement, human land use, population distributions, and cultural barriers
(inhibiting contact between cultures).
Physical
The land itself is worthy of our attention for just a moment. As you
probably well know, our earth consists of roughly 70% water (the oceans) and
only 30% actual dry land for us humans to hang out on. However small
it is, that quarter of our globe does much to influence the climate of our
fair earth. Three of the most important ways land affects climate distribution
and other physical systems are through the concepts of
CONTINENTALITY
ALTITUDINAL
ZONATION &
THE
RAIN SHADOW EFFECT
Cultural
In addition to affecting physical properties of climate and vegetation, physiography
influences many cultural properties of our world. Highland areas typically
serve to diminish contact and therefore diminish cultural influences on either
side of a mountain chain. In particular, think about how and why India's
culture is so distinct from the rest of East and Southeast Asia. How much
contact has historically taken place between Peru and Brazil? Why? Examine
the locations of the physical terrain features listed at the bottom of the
page in relation to the political borders of the countries in the world.
Which political borders are actually formed by mountains? Take a look at
France and Spain, at Chile and Argentina, at India and China--are all these
political borders just a coincidence? How has Switzerland been a politically
neutral country for 200 years? Are they just nice guys?
Mountains can and have served to effectively hamper movements of people,
trade, ideas and technology, armies, religions, and a variety of other physical
and cultural things. Where humans effectively penetrate mountain systems,
important links between cultures are created--like the Silk Road into China,
or even the Roman built road system of the first century AD which linked
Rome with all areas of its empire (modern day western Europe).
Okay, okay--now you understand the importance of terrain to understanding
life on our earth. But where it come from?
And where are the ones you should know about?
A mountain is a 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. The Earth's mountain ranges have been created by the collision of tectonic plates--part of a wider theory known as PLATE TECTONICS. The Himalayas, for example, developed from the collision of the Eurasian and Indian plates.
As you have now read about, associated with many mountain ranges are volcanoes. Volcanoes form where rising magma breaks through the Earth's surface. If the solidified magma of a volcano builds up, it can become a mountain like Mount St. Helens. If the collision involves two oceanic plates a string of volcanic mountains, an island arc, can form on the ocean floor. Earthquakes are also associated with the tectonic processes, but are a by-product of mountain building, not a contributor to mountain building.
Very rarely do mountains occur individually. In most cases, they are found in elongated ranges or chains. When an array of such ranges or chains are linked together, they constitute a mountain belt (e.g., the Andes and Rocky Mountains). The major mountain belts of the world belong to either of two enormous systems, the Circum-Pacific System or the Alpine-Himalayan System.
