Kimia's+Chapter+6+Section+3

__**Volcanic Landforms**__ __Key Terms__ -Shield Volcanoes-a wide,gently sloping mountain made of layers of lava;formed by quiet eruptions. -Cinder Cone-a steep-cone-shaped hill or small mountain made of volcanic ash,cinders,and bombs. -Composite Volcano-a tall,cone-shaped mountain in which layers of lava ans ash alternate. -Caldera-the large hole at the top of a volcano formed when the roof of magma chamber collapes. -Volcanic Neck-hardened magma in a volcano's pipe. -Dike-a slad of voclanic rock formed when magma forces itself across rock layers. -Sill-a slab of volcanic rock formed when magma squuzes between layers of rock. -Intrusion-An igneous rock layer formed when magma hardens beneath Earth's surface. -Batholith-a mass of rock formed when a large body of magma cools inside the crust.

Landforms From Lava and Ash Volcanic eruptions create landforms made of lava,ash,and other materials. Shield Vocanoes At some places on Earth's surface,thin layers of lava pours out of a vent and hardenon top of previous layers.Shield volcanoes created the Hawaiian Islands and the Medicine Lake volcano in northern California. Cinder Cone Volcanoes If a volcano's lava is high in silica ,it may produce ash,cinders,and bombs.For example,Paricutin in Mexico erupted in 1943 in a farmer's cornfield.The volcano built a cinder cone about 400 meters high. Composite Vocanoes Sometimes,lava flows alternate with explosive eruptions of ash,cinders,and bombsThe result is a composite.Examples include Ount Fuji in Japan and Mount Shasta and Lassen Peak in California. Lava Plateaus Some eruptions of lava form high,level areas called lava plateaus.First,lava flows out of several long cracks,cooling and solidifying.Again and again,floods of lava flow on top of earlier floods.After millions of years,these layers of lava can form high plateaus.Examples include the Columbia Plateau in Washington,Oregan,and Idaho,and the Modoc Plateau in the northeastern California. Calderas The huge hole left by the collapes of a volcanic moutnain is called a caldera.The hole is filled with the pieces of the volcano that have fallen inward,as well as some lava and ash.

Landforms From Magma Sometimes magma forces its way through cracks in the upper crust,but fails to reach the surface.There magma cools and hardens into rock.Over time,the forces that wear away Earth's surface-such as flowing water,ice,or wind-may strip away the layers above the hardened magma and finally expose it. Volcanic Necks A volcanic neck looks like a giant tooth stuck in the ground.A volcanic neck forms when magma hardens in the volcano's pipe.The softer rock around the pipe wears away,exposing the hard rock of the volcanic neck. Dikes and Sills Magma can force its way across or between rock layers.Magma that forces itself across rock layers hardens into a dike.Sometimes,a dike can be seen slanting through bedrock along a highway cut.When magma squeezes between horizontal layers of rock,it forms sill. Batholiths Large rock masses called batholiths form the core of many moutnain ranges.A batholith is a mass of rock formed when a large body of magma cools inside the crust.The Sierra Nevada batholith extends for roughly 600 kilometers along the eastern side of California.