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volcanoes

Chapter 7 Sections 3 & 4. volcanoes. Volcanic Eruptions. As magma heats up it becomes LESS dense and flows upwards. If there is an opening in the crust, it will reach the earth’s surface – a volcano is born!. Inside a volcano. ERUPTIONS.

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volcanoes

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  1. Chapter 7 Sections 3 & 4 volcanoes

  2. Volcanic Eruptions • As magma heats up it becomes LESS dense and flows upwards. • If there is an opening in the crust, it will reach the earth’s surface – a volcano is born!

  3. Inside a volcano

  4. ERUPTIONS • As magma rises the pressure surrounding it decreases. (It is not as deep anymore) This allows gases in and around the magma to expand. These expanding gases push the magma out of the volcano. • Eruptions can spew out Ash – fine dust specks Cinders – pebble-sized particles Bombs – baseball to car sized pieces!

  5. CINDERS ASH BOMBS!

  6. 2 types of eruptions • QUIET: magma low in silica; magma flows easily, gases bubble out slowly and gently. • EXPLOSIVE: magma high in silica; thick/sticky; doesn’t always flow out of the crater; can plug it like a cork; gases get trapped and build up pressure until they “explode”. PYROCLASTIC FLOW: when the volcano hurls out a mixture of hot gases, ash, cinders, and bombs.

  7. QUIET EXPLOSIVE

  8. SCARY PYROCLASTIC FLOW! Mt. Pinatubo Philippines 1991 eruption

  9. More pyroclastic flows

  10. Edge of a pyroclastic flow

  11. Pyroclastic flows cause tremendous damage!

  12. Volcano Hazards • Fire • Ash can bury towns • Landslides • Mudslides • Flooding (melted snow)

  13. Stages of Volcanic Activity Volcanoes are classified as: • ACTIVE – a live volcano that is erupting or will in the near future • DORMANT – “sleeping” may erupt again • EXTINCT – a dead volcano; unlikely to ever erupt again.

  14. TYPES OF VOLCANOES

  15. Click for the video clip!

  16. Other volcanic landforms • Lava plateau – lava flows out of several long cracks in an area and eventually over hundreds of years build up to form a plateau

  17. Calderas • Caldera – huge hole left by the collapse of volcano

  18. Soils from Lava & Ash When hardened lava erodes and forms soil, phosphorous, potassium and other important minerals are released. These make the soil very fertile.

  19. Dikes and Sills When magma forces itself across rock layers it hardens into a DIKE. When magma squeezes between horizontal layers of rock it forms a SILL.

  20. Dikes & Sills in New Zealand

  21. Volcanic Necks Forms when magma hardens in the volcano’s pipe and the softer rock surrounding it erodes away.

  22. Batholiths & Dome Mountains Batholith: large rock masses form the core of many mtn ranges; formed when a large body of magma cools inside the crust. Dome Mountain: smaller bodies of hardened magma

  23. Batholiths Sierra Batholith (Yosemite Nat’l Park)

  24. Dome Mountains

  25. Geothermal Activity • Geo – means “earth” • Therme – means “heat” • Geothermal is heat produced by the Earth (actually magma!) • Hot springs & Geysers are types of geothermal activity found in volcanic areas.

  26. In ARKANSAS In IDAHO Hot Springs

  27. GEYSERS (New Zealand)

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