TOPOGRAPHY
Topography is one of the fundamental data sets available to Earth scientists. The location of
mountains, ocean trenches, ridges, and coastlines are all keys to understanding Earth's dynamic
processes. You can examine the spatial relationships between areas of high topography, earthquakes,
and volcanoes, and consider how these relationships arise from plate interactions. The topographic
data set has a resolution of approximately 1 km, so you'll be able to see a variety of features related
to the underlying geology, geologic history and dynamic processes that create topography.
The shape of the Earth's surface is one of the most fundamental observations that we can make.
Observing topography can provide insight into processes acting deep within the Earth, as well as give
us clues about the geology and geologic history of an area.
Photo courtesy of NASA
Basin and Range Province, Nevada
Basin and Range Province, Nevada
Topography of the Basin and Range
province.
Topography of the Basin and Range Province
Topography and Tectonics
Why are some mountains very high, such as those in the Himalayas, while others--like the
Appalachians--are much lower? Mountains and all areas of high topography need to be maintained
by some sort of dynamic process. If not they will eventually erode and become flat plains. The
existence of regions of high topography tells us that some sort of tectonic process must be operating,
even if we cannot observe it directly.
Left:Location of Himalayan cross-section drawn in red on top of topography.
Right: Cross-sectional view of the Himalayas
In the Himalayan Mountains of Asia, two of the Earth's tectonic plates are converging. The Indian
plate is moving northward and colliding with the Asian plate. Because both India and Asia are made of
continental crust, which is thick and low-density, the plates buckle and bend, creating a thick and
deformed region of continent. This deformation is seen at the surface as the high peaks of the
Himalayas. The collision is accompanied by many earthquakes. Additionally, the high topography
above the surface is mirrored in the subsurface by a "crustal root," a region of thick crust extending
down into the mantle, just as the high mountains extend upward into the atmosphere.
Topography and Geology
The topography of a region is often strongly influenced by the underlying geology. For example, some
rock types are very resistant to erosion and form cliffs and ridges, while other rocks are softer and
easily eroded, forming valleys and slopes.
Topography and Isostasy
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