1. Chapter 8 VOLCANOES

2. Section 1 - Volcanic Eruptions  There are two types of volcanic eruptions, Nonexplosive and Explosive  1) NONEXPLOSIVE ERUPTIONS  When most people think about volcanic eruptions they think of rivers of red-hot lava (lava flows)  Lava flows come from nonexplosive eruptions  These calm outpourings of lava can release a HUGE amount of molten rock  Some of the LARGEST mountains in the world grew from repeated lava flows over hundreds of thousands of years  There are two types of volcanic eruptions, Nonexplosive and Explosive  1) NONEXPLOSIVE ERUPTIONS  When most people think about volcanic eruptions they think of rivers of red-hot lava (lava flows)  Lava flows come from nonexplosive eruptions  These calm outpourings of lava can release a HUGE amount of molten rock  Some of the LARGEST mountains in the world grew from repeated lava flows over hundreds of thousands of years

4.  2) EXPLOSIVE ERUPTIONS  During this type of eruption clouds of hot debris and gases SHOOT out of the volcano  This often happens at SUPERSONIC speeds  These eruptions do not produce lava flows  Instead molten rock is blown into millions of pieces that harden in the air  The dust size particles can circle the Earth for years in the upper atmosphere  This type of eruption can also blast millions of tons of solid rock from the volcano itself  In a matter of minutes, an explosive eruption can demolish rock formations that took thousands of years to build  In this case a volcano will actually shrink instead of grow  2) EXPLOSIVE ERUPTIONS  During this type of eruption clouds of hot debris and gases SHOOT out of the volcano  This often happens at SUPERSONIC speeds  These eruptions do not produce lava flows  Instead molten rock is blown into millions of pieces that harden in the air  The dust size particles can circle the Earth for years in the upper atmosphere  This type of eruption can also blast millions of tons of solid rock from the volcano itself  In a matter of minutes, an explosive eruption can demolish rock formations that took thousands of years to build  In this case a volcano will actually shrink instead of grow

8. Cross Section of a Volcano  All volcanoes share the same basic features  Magma - hot liquid material (rock) that creates volcanoes  Magma collects underground in Magma Chambers  Some chambers can be up to 160km below the surface  Vents - holes in the Earth through which magma rises  Lava - magma that erupts and flows onto the Earth’s surface  Pyroclastic Material - is magma that erupts as fragments of molten material that solidify in the air  Volcano - a vent or group of vents combined with the build up of lava and/or pyroclastic material  All volcanoes share the same basic features  Magma - hot liquid material (rock) that creates volcanoes  Magma collects underground in Magma Chambers  Some chambers can be up to 160km below the surface  Vents - holes in the Earth through which magma rises  Lava - magma that erupts and flows onto the Earth’s surface  Pyroclastic Material - is magma that erupts as fragments of molten material that solidify in the air  Volcano - a vent or group of vents combined with the build up of lava and/or pyroclastic material

10. Magma  By comparing the composition of magma from different types of eruptions, scientists have determined that the composition of the magma dictates whether an eruption will be nonexplosive, explosive, or somewhere in between  Water  A volcano is more likely to erupt explosively if the magma has a high water content  The more water there is in magma, the greater the pressure (like a can of soda) and the greater chance that there will be a violent eruption  Gases (steam) need more room than liquids (pressure)  By comparing the composition of magma from different types of eruptions, scientists have determined that the composition of the magma dictates whether an eruption will be nonexplosive, explosive, or somewhere in between  Water  A volcano is more likely to erupt explosively if the magma has a high water content  The more water there is in magma, the greater the pressure (like a can of soda) and the greater chance that there will be a violent eruption  Gases (steam) need more room than liquids (pressure)

11.  Silica - Explosive eruptions are also caused by magma that contains a large percentage of silica  Silica rich magma is very thick and has a tendency to harden inside the volcano  This causes magma and gases to get trapped inside the volcano until so much pressure builds up that the volcano goes BOOM !!!!!!  Low silica magma is runny which allows gases to escape easily, keeping pressure low  Silica - Explosive eruptions are also caused by magma that contains a large percentage of silica  Silica rich magma is very thick and has a tendency to harden inside the volcano  This causes magma and gases to get trapped inside the volcano until so much pressure builds up that the volcano goes BOOM !!!!!!  Low silica magma is runny which allows gases to escape easily, keeping pressure low

12. What Erupts from a Volcano?  Nonexplosive eruptions produce mostly lava, while explosive eruptions produce mostly pyroclastic material  Over many years, a volcano may alternate between eruptions that produce lava or pyroclastic material  Eruptions of lava and pyroclastic material may also occur as separate stages of a single eruption event  Nonexplosive eruptions produce mostly lava, while explosive eruptions produce mostly pyroclastic material  Over many years, a volcano may alternate between eruptions that produce lava or pyroclastic material  Eruptions of lava and pyroclastic material may also occur as separate stages of a single eruption event

13.  Lava  Lava is magma that flows onto the Earth’s surface  Like magma lava ranges in consistency from thick to thin  Blocky Lava is cool, stiff lava that cannot travel far from the erupting vent  Blocky lava forms jumbled heaps of sharp edged chunks  Pahoehoe is lava that flows slowly, like wax dripping from a candle forming a glassy surface with round wrinkles that look like “ropes”  Aa is slightly stiffer lava that pours out quickly and forms a brittle crust that can break and harden into jagged pieces  Pillow Lava forms when lava erupts underwater  It forms rounded lumps that are the size and shape of pillows  Lava  Lava is magma that flows onto the Earth’s surface  Like magma lava ranges in consistency from thick to thin  Blocky Lava is cool, stiff lava that cannot travel far from the erupting vent  Blocky lava forms jumbled heaps of sharp edged chunks  Pahoehoe is lava that flows slowly, like wax dripping from a candle forming a glassy surface with round wrinkles that look like “ropes”  Aa is slightly stiffer lava that pours out quickly and forms a brittle crust that can break and harden into jagged pieces  Pillow Lava forms when lava erupts underwater  It forms rounded lumps that are the size and shape of pillows

15.  Pyroclastic Material  Pyroclastic material refers to the rock fragments created by explosive volcanic eruption and is produced when magma EXPLODES from a volcano and solidifies in the air. It can come in a variety of sizes that include:  Volcanic Blocks - are the largest pieces upwards to the size of a house  Volcanic blocks are large pieces of rock (not magma) from the mountain  Volcanic Bombs - are large blobs of magma that harden in a flattened, elongated shape, like a bomb  Volcanic bombs are greater than 64mm in diameter  Lapilli - which means “little stones” in Italian, are pebble like bits of pyroclastic material between 2 and 64mm in diameter  Volcanic Ash - consist of particles that are less than 2mm in diameter  Pyroclastic Material  Pyroclastic material refers to the rock fragments created by explosive volcanic eruption and is produced when magma EXPLODES from a volcano and solidifies in the air. It can come in a variety of sizes that include:  Volcanic Blocks - are the largest pieces upwards to the size of a house  Volcanic blocks are large pieces of rock (not magma) from the mountain  Volcanic Bombs - are large blobs of magma that harden in a flattened, elongated shape, like a bomb  Volcanic bombs are greater than 64mm in diameter  Lapilli - which means “little stones” in Italian, are pebble like bits of pyroclastic material between 2 and 64mm in diameter  Volcanic Ash - consist of particles that are less than 2mm in diameter

16. Chapter 8 Quiz 1  1) __________ is the hot liquid material found deep in the ground, and is the driving force that creates volcanoes  2) __________ are holes in the Earth’s crust in which the above material (#1) flows  3) __________ includes hot liquid material (#1) and rock fragments that are BLASTED into the air  4) __________ are large pieces of rock (from the mountain) that are blasted into the air, and can be upwards of the size of a house  5)___________ is lava that hardens into jagged pieces  Bonus) _________ forms when a magma chamber collapses causing the “roof” above it to collapse  1) __________ is the hot liquid material found deep in the ground, and is the driving force that creates volcanoes  2) __________ are holes in the Earth’s crust in which the above material (#1) flows  3) __________ includes hot liquid material (#1) and rock fragments that are BLASTED into the air  4) __________ are large pieces of rock (from the mountain) that are blasted into the air, and can be upwards of the size of a house  5)___________ is lava that hardens into jagged pieces  Bonus) _________ forms when a magma chamber collapses causing the “roof” above it to collapse

17. Section 2 - Volcanoes Effects on Earth  The effects of volcanic eruptions can be seen both on land (mountains, plateaus, etc.) and in the air (ash and escaping gases)  Ash and escaping gases can affect global climate patterns  The effects of volcanic eruptions can be seen both on land (mountains, plateaus, etc.) and in the air (ash and escaping gases)  Ash and escaping gases can affect global climate patterns

18. An Explosive Impact  Because ash and gases can be ejected high into the air it can have widespread effects on Earth, including blocking out the sun for days and over thousands of miles.  Ash can also blow down trees and knock down buildings  Flows - are clouds of hot ash that can flow rapidly downhill like an avalanche, searing everything in its path  Large amounts of ash can sometimes mix with water, turning the flow into the consistency of wet cement  These flows can pick up boulders, trees, and buildings causing MASSIVE destruction  Because ash and gases can be ejected high into the air it can have widespread effects on Earth, including blocking out the sun for days and over thousands of miles.  Ash can also blow down trees and knock down buildings  Flows - are clouds of hot ash that can flow rapidly downhill like an avalanche, searing everything in its path  Large amounts of ash can sometimes mix with water, turning the flow into the consistency of wet cement  These flows can pick up boulders, trees, and buildings causing MASSIVE destruction

20.  Fallout - happens when volcanic ash falls back to the ground  Buildings have been known to collapse under the weight of accumulating ash  Ash can also dam up river valleys, resulting in MASSIVE floods  Too much ash can smoother crops causing food shortages and loss of livestock  Climatic Fluctuation - are changes in global temperatures and moisture levels due to the release of ash and sulfur rich gases that reach our upper atmosphere  Temperature shifts can disrupt climates all over the world causing milder wetter summers and longer harsher winters resulting in starvation and disease  Fallout - happens when volcanic ash falls back to the ground  Buildings have been known to collapse under the weight of accumulating ash  Ash can also dam up river valleys, resulting in MASSIVE floods  Too much ash can smoother crops causing food shortages and loss of livestock  Climatic Fluctuation - are changes in global temperatures and moisture levels due to the release of ash and sulfur rich gases that reach our upper atmosphere  Temperature shifts can disrupt climates all over the world causing milder wetter summers and longer harsher winters resulting in starvation and disease

22. Different Types of Volcanoes  There are three basic types of volcanoes:  1) Shield Volcanoes - are volcanoes built out of layers of lava from repeated nonexplosive eruptions  Because lava is runny it spreads out over a wide area, which over time builds up to form volcanoes with wide bases and gently sloping sides  Though their sides are not steep, shield volcanoes can be enormous and include the largest mountain on Earth, Mauna Kea in Hawaii  2) Cinder Cone Volcanoes - are small volcanic cones made entirely of pyroclastic material from moderately explosive eruptions  These volcanoes have narrow bases and steeper slopes  Cinder cone volcanoes usually erupt for a short period of time and occur in clusters  These volcanoes erode quickly because the pyroclastic material of the volcano is not cemented together by lava  3) Composite Volcanoes - form from explosive eruptions of pyroclastic material, followed by quieter outpourings of lava  These are the most common types of volcanoes and are also known as stratovolcanoes  These have broad bases and sides that get steeper toward the summit  There are three basic types of volcanoes:  1) Shield Volcanoes - are volcanoes built out of layers of lava from repeated nonexplosive eruptions  Because lava is runny it spreads out over a wide area, which over time builds up to form volcanoes with wide bases and gently sloping sides  Though their sides are not steep, shield volcanoes can be enormous and include the largest mountain on Earth, Mauna Kea in Hawaii  2) Cinder Cone Volcanoes - are small volcanic cones made entirely of pyroclastic material from moderately explosive eruptions  These volcanoes have narrow bases and steeper slopes  Cinder cone volcanoes usually erupt for a short period of time and occur in clusters  These volcanoes erode quickly because the pyroclastic material of the volcano is not cemented together by lava  3) Composite Volcanoes - form from explosive eruptions of pyroclastic material, followed by quieter outpourings of lava  These are the most common types of volcanoes and are also known as stratovolcanoes  These have broad bases and sides that get steeper toward the summit

24. Craters and Calderas  Crater - is a funnel shaped pit found at the top of the central vent in most volcanoes  A craters funnels shape results from explosions of material out of the vent, as well as the collapse of material from the craters rim back into the vent  Caldera - forms when a magma chamber that supplies material to a volcano empties and its roof collapses  This causes the ground to sink, leaving a large circular depression  Crater - is a funnel shaped pit found at the top of the central vent in most volcanoes  A craters funnels shape results from explosions of material out of the vent, as well as the collapse of material from the craters rim back into the vent  Caldera - forms when a magma chamber that supplies material to a volcano empties and its roof collapses  This causes the ground to sink, leaving a large circular depression

26. Lava Plateaus  Most of the lava on Earth’s continents do NOT come from volcanoes, but ooze from a series of long cracks called fissures  Runny lava oozing from fissures can spread out over thousand of square kilometers forming Lava Plateau  i.e. The Columbia River Plateau formed about 15 million years ago  Most of the lava on Earth’s continents do NOT come from volcanoes, but ooze from a series of long cracks called fissures  Runny lava oozing from fissures can spread out over thousand of square kilometers forming Lava Plateau  i.e. The Columbia River Plateau formed about 15 million years ago

28. Chapter 8 Quiz 2  1) _________ are clouds of hot ash that can flow rapidly downhill like an avalanche  2) _________ are built out of layers of lava from repeated nonexplosive eruptions  3)__________ are also referred to as Statovolcanoes  4) __________ forms when a magma chamber empties and its roof collapses  Bonus) _________ are places within tectonic plates where columns of rising magma are  1) _________ are clouds of hot ash that can flow rapidly downhill like an avalanche  2) _________ are built out of layers of lava from repeated nonexplosive eruptions  3)__________ are also referred to as Statovolcanoes  4) __________ forms when a magma chamber empties and its roof collapses  Bonus) _________ are places within tectonic plates where columns of rising magma are

29. Section 3 - What Causes Volcanoes  The Formation of Magma  The key to understanding why volcanoes erupt is understanding how magma forms  All volcanoes begin when magma collects in pockets in the deep regions of the Earth’s crust and uppermost layers of the mantle  The zone of magma formation is between 25 - 160 km below the surface  Although the rocks of the mantle are hot and pliable, it is still not a liquid. Why?  The weight of the rock above the mantle exerts so much PRESSURE that the atoms are forced close together  This increases the melting point (temperature point) at which the rock will melt  Mantle rock will not melt (turn into magma) until the temperature increases or the pressure on it releases  Because the temperature of the mantle is fairly constant, pressure release is the main reason why rock melts  The Formation of Magma  The key to understanding why volcanoes erupt is understanding how magma forms  All volcanoes begin when magma collects in pockets in the deep regions of the Earth’s crust and uppermost layers of the mantle  The zone of magma formation is between 25 - 160 km below the surface  Although the rocks of the mantle are hot and pliable, it is still not a liquid. Why?  The weight of the rock above the mantle exerts so much PRESSURE that the atoms are forced close together  This increases the melting point (temperature point) at which the rock will melt  Mantle rock will not melt (turn into magma) until the temperature increases or the pressure on it releases  Because the temperature of the mantle is fairly constant, pressure release is the main reason why rock melts

30. Where Volcanoes Form  Most volcanoes are found on tectonic plate boundaries  These boundaries are where plates either collide or separate from each other  The plate boundaries around the Pacific Ocean is called the RING OF FIRE !!!!!!  At these types of boundaries it is easier for magma to travel upward through the crust  Most volcanoes are found on tectonic plate boundaries  These boundaries are where plates either collide or separate from each other  The plate boundaries around the Pacific Ocean is called the RING OF FIRE !!!!!!  At these types of boundaries it is easier for magma to travel upward through the crust

31. When Tectonic Plates Separate  As two tectonic plates separate a deep crack, called a rift, forms  Mantle material is then able to rise up, decreasing the pressure on it, and causing it to melt and turn into magma  Magma continuously rises up through the rift creating new crust  Most divergent boundaries are found under the oceans where they produce long underwater mountain chains called mid-ocean ridges  As two tectonic plates separate a deep crack, called a rift, forms  Mantle material is then able to rise up, decreasing the pressure on it, and causing it to melt and turn into magma  Magma continuously rises up through the rift creating new crust  Most divergent boundaries are found under the oceans where they produce long underwater mountain chains called mid-ocean ridges

33. When Tectonic Plates Collide  The place where two tectonic plates collide is called a convergent boundary  The movement of one plate under another is called a subduction zone  Convergent boundaries are commonly located where oceanic plates collide with continental plates  As the oceanic plate slides under the continental plate it sinks deeper into the mantle causing it to melt  As the magma rises to the surface it cause the silica rich continental crust to also melt becoming part of the gooey lava that can cause an explosive eruption  The place where two tectonic plates collide is called a convergent boundary  The movement of one plate under another is called a subduction zone  Convergent boundaries are commonly located where oceanic plates collide with continental plates  As the oceanic plate slides under the continental plate it sinks deeper into the mantle causing it to melt  As the magma rises to the surface it cause the silica rich continental crust to also melt becoming part of the gooey lava that can cause an explosive eruption

34. Hot Spots  Not all magma develops along tectonic plate boundaries  i.e. The Hawaiian Islands are formed over hot spots  Hot Spots - are places within tectonic plates that are directly above columns of rising magma called mantle plumes  Not all magma develops along tectonic plate boundaries  i.e. The Hawaiian Islands are formed over hot spots  Hot Spots - are places within tectonic plates that are directly above columns of rising magma called mantle plumes