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Structure consists of the materials that a landform is made of, and the manner in which these materials are arranged. For example, is a mountain made primarily of granite, sandstone, copper, or of some other material. Is that material arranged in horizontal layers, vertical layers, or in some other configuration.

 

A landform is a natural feature on the Earth's surface that is part of the terrain. Mountains, hills, plateaus, and plains are the four major types of landforms. Minor landforms includebuttes, canyons, valleys, and basins. Submerged features include mid-ocean ridges, volcanoes, and the greatocean basins.

Tectonic plate movement under the Earth can create landforms by pushing up mountains and hills. Erosion by water and wind can wear down land and create landforms like valleys and canyons. Both processes happen over a long period of time.  The Colorado River carved out the Grand Canyon in the U.S. state of Arizona. The Grand Canyon is 446 kilometers (277 miles) long.  The highest landform on Earth is a mountain: Mount Everest in Nepal. It measures 8,850 meters (29,035 feet) above sea level. It is part of the Himalaya range that runs across several countries in Asia.  Landforms can exist under water in the form of mountain ranges and basins under the sea. The Mariana Trench, the deepest landform on Earth, is in the South Pacific Ocean.

 

Landforms are categorized by characteristic physical attributes such as elevation, slope, orientation, stratification, rock exposure, and soil type.  Gross physical features or landforms include intuitive elements such as berms, mounds, hills, ridges, cliffs, valleys, rivers, peninsulas and numerous other structural and size-scaled (i.e. ponds vs. lakes, hills vs. mountains) elements including various kinds of inland and oceanic waterbodies and sub-surface features.

 

Oceans and continents exemplify the highest-order landforms. Landform elements are parts of a high-order landforms that can be further identified and systematically given a cohesive definition such as hill-tops, shoulders, saddles, foreslopes and backslopes.  Some generic landform elements including: pits, peaks, channels, ridges, passes, pools and plains.  

 

Terrain (or relief) is the third or vertical dimension of land surface. Topography is the study of terrain, although the word is often used as a synonym for relief itself. When relief is described underwater, the term bathymetry is used. In cartography, many different techniques are used to describe relief, including contour lines and TIN (Triangulated irregular network).  Elementary landforms (segments, facets, relief units) are the smallest homogeneous divisions of the land surface, at the given scale/resolution. These are areas with relatively homogeneous morphometric properties, bounded by lines of discontinuity. A plateau or a hill can be observed at various scales ranging from few hundred meters to hundreds of kilometers. Hence, the spatial distribution of landforms is often scale-dependent as is the case for soils and geological strata.

 

A number of factors, ranging from plate tectonics to erosion and deposition, can generate and affect landforms. Biological factors can also influence landforms— for example, note the role of vegetation in the development of dune systems and salt marshes, and the work of corals and algae in the formation of coral reefs.  Landforms do not include man-made features, such as canals, ports and many harbors; and geographic features, such as deserts, forests, and grasslands.

 

Many of the terms are not restricted to refer to features of the planet Earth, and can be used to describe surface features of other planets and similar objects in the Universe. Examples are mountains, hills, polar caps, and valleys, which are found on all of the terrestrial planets.

 

Landform Process

 

Process is all of the forces that combined to form the landform. These processes might be weather, pressure, water, wind, moving sheets of ice, etc.  All landforms are being changed by the many different forces that are constantly at work on them. The steepness of a landform’s slope gives geologists important clues about its formation, and structure. Slope also influences the evolution of landforms.  Drainage is considered separately from other processes, because it is so influential. How quickly water drains away from a landform impacts the overall shape and evolution of that landform tremendously.

 

Huge Ocean Discovered Inside Earth

 

Scientists probing the Earth's interior have found a large reservoir of water equal to the volume of the Arctic Ocean beneath eastern Asia. The left figure is a slice through the Earth, taken from the figure on the right, showing the attenuation anomalies within the mantle at a depth of roughly 620 miles. In both images, red shows unusually soft and weak rock believed to be saturated with water, and the blue shows unusually stiff rock (yellow and white show near-average values).

 

Scientists scanning the deep interior of Earth have found evidence of a vast water reservoir beneath eastern Asia that is at least the volume of the Arctic Ocean.  The discovery marks the first time such a large body of water has found in the planet's deep mantle. The finding, made by Michael Wysession, a seismologist at Washington University in St. Louis, and his former graduate student Jesse Lawrence, now at the University of California, San Diego, will be detailed in a forthcoming monograph to be published by the American Geophysical Union.

 

Looking down deep

 

The pair analyzed more than 600,000 seismograms — records of waves generated by earthquakes traveling through the Earth—collected from instruments scattered around the planet. [Image Gallery: This Millennium's Destructive Earthquakes]

They noticed a region beneath Asia where seismic waves appeared to dampen, or "attenuate," and also slow down slightly. "Water slows thespeed of waves a little," Wysession explained. "Lots of damping and a little slowing match the predictions for water very well."

 

Previous predictions calculated that if a cold slab of the ocean floor were to sink thousands of miles into the Earth's mantle, the hot temperatures would cause water stored inside the rock to evaporate out.  "That is exactly what we show here," Wysession said. "Water inside the rock goes down with the sinking slab and it's quite cold, but it heats up the deeper it goes, and the rock eventually becomes unstable and loses its water."  The water then rises up into the overlying region, which becomes saturated with water [image]. "It would still look like solid rock to you,” Wysession told LiveScience. "You would have to put it in the lab to find the water in it."  Although they appear solid, the composition of some ocean floor rocks is up to 15 percent water. "The water molecules are actually stuck in the mineral structure of the rock," Wysession explained. "As you heat this up, it eventually dehydrates. It's like taking clay and firing it to get all the water out."

 

The researchers estimate that up to 0.1 percent of the rock sinking down into the Earth's mantle in that part of the world is water, which works out to about an Arctic Ocean's worth of water.  "That's a real back of the envelope type calculation," Wysession said. "That's the best that we can do at this point."  The Beijing anomaly Wysession has dubbed the new underground feature the "Beijing anomaly," because seismic wave attenuation was found to be highest beneath the Chinese capital city. Wysession first used the moniker during a presentation of his work at the University of Beijing.  "They thought it was very, very interesting," Wysession said. "China is under greater seismic risk than just about any country in the world, so they are very interested in seismology."

 

Water covers 70 percent of Earth's surface and one of its many functions is to act like a lubricant for the movement of continental plates.  "Look at our sister planet, Venus," Wysession said. "It is very hot and dry inside Venus, and Venus has no plate tectonics. All the water probably boiled off, and without water, there are no plates. The system is locked up, like a rusty Tin Man with no oil."  The Earth’s radius is about 4,000 miles (6,400 kilometers). The main layers of its interior are in descending order: crust, mantle and core. The crust thickness averages about 18 miles (30 kilometers) under the continents, but is only about 3 miles (5 kilometers) under the oceans. It is light and brittle and can break. In fact it's fractured into more than a dozen major plates and several minor ones. It is where most earthquakes originate.The mantle is more flexible – it flows instead of fractures. It extends down to about 1,800 miles (2,900 kilometers) below the surface.The core consists of a solid inner core and a fluid outer core. The fluid contains iron, which, as it moves, generates the Earth’s magnetic field. The crust and upper mantle form the lithosphere, which is broken up into several plates that float on top of the hot molten mantle below.