3.4 Volcanic Landforms

1. 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.

2. 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

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

4. 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

5. 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

6. 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

7. 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

9. 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

10. 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

11. 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

12. sill dike • 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

13. 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

14. 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

15. 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

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

17. 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

18. 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. • Geothermal Energy • Heated water can provide an energy source • Heated water can be used to power turbines and create electricity