3 4 Volcanic Landforms Objectives List the landforms

3. 4 Volcanic Landforms Objectives: List the landforms that lava and ash create Explain how magma that hardens beneath earth’s crust creates landforms Identify other distinct features that occur in volcanic areas Volcanic activity on and beneath the surface has built up Earth’s land areas.

Landforms from Lava and Ash Volcanic eruptions create landforms made of lava, ash and other materials Shield volcanoes Cinder cone volcanoes Composite volcanoes Lava plateaus Another landform results from the collapse of a volcanic mountain caldera

Shield volcanoes Gently Thin sloping mountains layers of low viscosity lava build up over time Ex) the Hawaiian Islands Shield Volcano in Iceland

Cinder cone volcanoes High viscosity lava produces ash, cinders and bombs Those materials build up around the vent in a steep cone shaped hill/mountain. Ex) Sunset Crater in Arizona

Composite Volcanoes Form when volcanoes alternate between lava flows and explosive eruptions of ash, cinders and bombs. Tall cone shaped mountain with alternate layers of ash and lava. Ex. Mt. St. Helens, Washington and Mt. Fuji, Japan.

Composite Volcanoes Form when volcanoes alternate between quiet lava flows and explosive eruptions of ash, cinders and bombs Tall, cone shaped mountain with alternating layers of ash and lava Ex) Mt St. Helens, Washington and Mt. Fuji, Japan

Lava Plateaus Low viscosity lava flows out of several long cracks and travels far before cooling After Ex) millions of years a high plateau forms Columbia Plateau in Washington, Oregon and Idaho

Calderas Huge hole left by the collapse of composite volcanic mountains Filled with fallen pieces of the volcano, ash and lava Enormous eruptions may empty the pipe and the magma chamber there is only hollow space left that can’t support the weight and it collapses on itself Overtime water from rain and snow may fill the caldera Ex) Crater Lake, Oregon

Soil from lava and ash People settle near volcanoes because of the rich, fertile soil At first, after volcanic eruptions the land is empty and barren Overtime the ash breaks down and provides: Potassium Phosphorus Other substances that plants need

Landforms from Magma Sometimes magma forces its way through cracks in the crust but never reaches the surface The magma cools and hardens within the rock layers Overtime ice, wind, or rain erode away the surrounding rock and expose the hardened magma

Volcanic Forms Necks when magma hardens in the pipe Overtime Looks Ex) the outer rock is weathered away like a giant tooth Ship Rock, New Mexico

Dikes and Sills Dike: when magma forces its way across multiple rock layers and hardens Sill: when magma squeezes between horizontal layers of rock and hardens Ex) Palisades, NY & NJ sill

Batholiths Large masses of rock that are formed when a huge mass of magma cools inside the Earth’s crust The outer layers of rock erode away leaving the hardened magma exposed Ex) Sierra Nevada Batholith

Dome Mountains Created by smaller bodies of magma The hardened magma uplifts the surrounding rock and causes it to bend into a dome shape Ex) Black Hills, South Dakota

Geothermal Activity Geo = Earth, therme = heat Geothermal activity – when magma a few km beneath the surface heats underground water. Ex) hot springs and geysers found near past and present volcanic activity

Hot Springs Forms when underground water is heated by magma or hot rock The heated water rises and collects in pools

Geysers Fountains of water and steam that erupt from the ground The heated water and steam build up pressure until finally it erupts Ex) Old Faithful, Yellowstone National Park

Geothermal Energy Heated water can provide an energy source Heated water can be used to power turbines and create electricity A panoramic view of the Geysers geothermal power plant in Geysers, Calif. The site, located above Santa Rosa, is the largest geothermal development in the world.