What landforms are formed by volcanoes?
In violent fashion, volcanic vents mark where molten rock reaches the Earth's surface.From subtle fissures to skyscraping peaks, these landforms are both destructive and constructive: They can smother terrain and ecosystems with lava, mudflows and ash, but also nourish biological communities with fertile soil and create new topographic features.
Sometimes subtle, sometimes unmistakable and dramatic, volcanoes are landforms.The image of a volcano is derived from intermixed layers of lava, ash and other "pyroclastic" materials accumulated over many eruptions and emissions.A shield volcano, such as the enormous Mauna Kea in Hawaii, assumes a gentle slope from basaltic lava.The shape of cinder cones and lava domes may be assumed by the volcano.Where weathering and erosion have stripped outer layers from extinct volcanoes, all that is left on the landscape are resistant remnants of their "throats" and conduits in the form of volcanic plugs and dikes.New Mexico's Shiprock is a world-famous example of the former.Volcanic seamounts and island arcs are major features in the oceans.
The opening of the conduit is called a volcanic crater.At the main summit of a volcano, it is a relatively small concavity marking a vent.A caldera is a ruined crater formed from an explosion or the emptying of a magma chamber.The Spanish call it a cauldron.These depressions can be as wide as 10 miles and as broad as 16 kilometers.The caldera that is Oregon's Crater Lake was created by the eruption of Mount Mazama 7,700 years ago.The volcano, despite its blasted mouth, is often shown to be far from dead when new volcanic cones form within a caldera.
The spread and petrification of their magma and other pyroclastic materials has led to the creation of landforms far from their vents.Flood basalts can build huge lava plateaus that cover thousands of square kilometers.The Columbia Plateau in the northwestern United States is an example.Existing river drainages are often followed by lava flows.The flow, now a ridge, may create an inverted valley if weaker rock erodes away.
There is never a vacuum when it comes to a volcano's influence on a landscape.The interaction with other land-sculpting factors can produce distinctive features.The carving work of ice mass counteracts the mountain-building action of active eruptions.glaciers have gnawed a craggy cone of its summit, but Mount Jefferson is not extinct, for example.As fresh-flowing lava and ice meet, the mesa-like mountains called tuyas, produce their own characteristic landforms.A shield volcano supports a distinctive drainage with streams dropping on all sides from the central summit.