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 sloping mountains  Thin 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 millions of years a high plateau forms  Ex) 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 Necks  Forms when magma hardens in the pipe  Overtime the outer rock is weathered away  Looks like a giant tooth  Ex) 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 dike 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.