Plate Tectonics and Mountain Building

 Three most common types of mountains:  Fault-block mountains  Folded mountains  Volcanic mountains

 Formed when rock layers are compressed (squeezed) by horizontal pressure and pushed upward.  Usually form at convergent plate boundaries  continental/continental  Ex. Himalayas

 Caused by tension (stretching) that causes large blocks of the Earth’s crust to fault (break) and then drop relative to each other  Formed at divergent boundaries  Jagged peaks  Ex. Sierra Nevada in California

 Molten rock (lava) erupts onto the Earth’s surface  Creates new crust  Located at:  convergent boundaries  Divergent boundaries  “hot spots”

 Sometimes called strato volcanoes  Formed by alternating layers of lava and rock  Their snow-capped peaks often exceed 2500m in height  Erupt in explosive way due to viscous magma  Mt. Fuji in Japan and Mt. St. Helens are examples

 Built out of layers of runny lava  Forms a huge broad shaped, gently sloping cone  Eruptions are usually not violent due to basaltic lava  Hawaii is an example

 Small volcanic cones usually found on the sides of strato and shield volcanoes  Built out of pyroclastic material  Eruptions usually do not cause loss of life  Grow rapidly and are generally found in clusters  They erode quickly due to the material they are made out of

 Magma is mostly made out of silica (a compound of silicon and oxygen)  Magma high in silica resists flowing and therefore create violent eruptions  Rhyolite magma contains 75% silica and erupts around C ( F)  Magma low in silica flows easily  Basalt magma contains 50% silica and erupts around 1200 C (2192 F)

 Produced from silica poor magma  Produces lava flows  Shield volcanoes produce these types of eruptions

 Have pyroclastic flows with them  Do not generally produce lava flows  Gases and debris can stay in the atmosphere for years  Can change the climate in the area for years

 Lava Flows  Knock down, cover, or burn nearly everything in its path  Volcanic Ash  Can cause roofs to collapse, make roads slippery, clog engines  Mudflows  Can bury towns  Pyroclastic flows  Can knock down everything in its path  Landslides  Can destroy things in its path  Can start a Tsunami  Steam Explosion  Uncommon but can be very devastating

 Effects can last for many years  Mudflows can occur years later  The new crust that forms is very rich in nutrients  Makes wonderful farm land  Can make beautiful landscape to live by

 Increasing the amount of carbon dioxide in the air  Releases sulfur dioxide into the air which creates acid rain  Can change the weather of the world  Large amounts of gases and volcanic ash can cause a haze blocking out the sun and lowering the global temperature for years

 Hot springs  Magma in the Earth heats water for a hot spring  Geyser  Some hot springs have enough pressure that they erupt out of the ground  Old Faithful in Yellowstone National Park erupts every 35 minutes to 2 hours  Fumarole  Similar to a geyser but releases steam and other gases  Changes in hot springs and fumaroles help predict explosions

 Hot springs that form at spreading centers in the ocean  Bring out dissolved minerals and heat  Allow sea animals to live where they normally couldn’t