What is Inside a Volcano?

Transcription

1 Volcanoes

2 What is Inside a Volcano? A magma chamber filled with molten rock deep underground that feeds the volcano Magma is released through vents during an eruption

3 Types of Volcanic Eruptions Non-Explosive & Explosive Non-explosive eruptions are the most common Have calm lava flows Can release huge amounts of lava A lot of the sea floor and NW U.S. are covered with lava Pu'u O'o volcano in Hawaii Eruption Video 1 Eruption Video 2 Eruption Video 3

4 Types of Volcanic Eruptions Explosive Explosive eruptions are rare Clouds of hot ash and gas shoot out Molten rock is blown out and cooled into ash Ash = tiny pieces of rock, minerals and glass Mt. Saint Helens, Washington State 1980 Best Explosive Eruptions Video

5 The Types of Magma is Important Water and Magma = Explosive Eruptions Underground, water is dissolved in magma If magma rises quickly, the decrease in pressure causes water and other compounds (CO 2 ) to become gases The gases expand rapidly and explode This is similar to shaking a can of soda The dissolved CO2 is released, the pressure Builds up, and when the can is opened, soda shoots out

6 The Types of Magma is Important Silica and Magma = Explosive Eruptions Silica is a hard colorless compound that occurs as the mineral quartz Found mostly in Sandstone Silica Grains Silica Gel Quartz Sandstone

7 The Types of Magma is Important Silica and Magma = Explosive Eruptions Silica-rich magma flows slowly and hardens in a volcano s vents, plugging it As magma builds up behind it, pressure increases until it explodes Magma with less silica is more fluid, less likely to plug the vents, and less likely to cause explosive eruptions

8 What Erupts from a Volcano? Lava Molten rock made up of a slush of crystals, liquids and bubbles Mostly Silicon, Oxygen, Aluminum and Iron Lava Video Pyroclastic Flow Material formed when magma blasts into the air and hardens Move 100 mph and faster Can rise thousands of feet Reach 800 to 2000 F Pyroclastic Flow Video

9 What s the Difference Between Magma & lava? Magma = molten rock under the Earth Lava = molten rock above the Earth = The rock that forms after lava cools They are really the same thing, one is just above, the other is below

10 Viscosity of Lava Viscosity is how well something flows Milk = Low viscosity Milkshake = High viscosity The viscosity of Lava affects its surface & appearance Viscosity gives rise to different types of Lava

11 Types of Lava There are 4 main types of Lava Aa Pahoehoe Pillow Lava Blocky Lava Ah Ah Pa ho ho

12 Aa Hawaiian for stony rough lava & to burn Has a High viscosity = flows slowly The crust is torn into jagged pieces as lava flows underneath Is so named because of the painful experience of walking barefoot across its hot jagged surface Aa Lava Flow Video Kilauea Volcano, Hawaii

13 Pahoehoe Hawaiian for smooth, unbroken lava Has a Lower viscosity = flows more quickly Has a shiny, smooth, glassy surface Coke Vs. Pahoehoe Video Monster Energy Vs. Pahoehoe

14 Pillow Lava Forms from underwater eruptions Very common The lava gets a solid crust when hitting the water, the crust cracks & oozes out a large blob or pillow Pillow Lava Eruption

15 Blocky Lava Blocky lava = cool, stiff lava that doesn t travel far Oozes from a volcano and forms jumbled heaps of sharp-edged chunks Blocky Lava Video

16 Types of Pyroclastic Material There are 4 main types of Pyroclastic Material Volcanic Volcanic Lapilli Volcanic Blocks Bombs Ash

17 Volcanic Blocks Large pieces of solid rock erupted from a volcano The 1924 eruption in Kilauea, Hawaii, threw rocks weighing up to 14 tons 3000 feet (10 football fields) There were multiple reports of people being hit and crushed by flying rocks

18 Volcanic Bombs Large blobs of magma that harden in the air Usually flatten out because they spin in the air Can explode from the gas pressure inside as they cool Volcanic Blocks & Volcanic Bombs Video

19 Lapilli Means little stones in Latin Must be less than 2.5 inches Anything larger are Volcanic Blocks & Bombs Pele s Tears are a type of Lapilli which looks like tear drops. Lava in the air can form teardrop-shaped glass lapilli. Named after Pele, the Hawaiian goddess of fire.

20 Volcanic Ash Forms when gas in magma expands & the walls of the bubbles explode into tiny glass slivers Ash makes up most of a pyroclastic flow Very fine ash can stay in the atmosphere for years and travel around the planet by wind currents Effects of Volcanic Ash - Video

21 Types of Volcanoes There are 3 main types of Volcanoes: Shield Cinder Cone Composite

22 Shield Volcanoes Built of layers of lava from many non-explosive eruptions Because the lava is runny, the volcano spreads out over a wide area, creating gently sloping sides Mauna Loa, in Hawaii is 4,000 feet above sea level

23 Cinder Cone Volcanoes Smallest and most abundant volcanoes Are active for only a short time then go dormant Made of layers of ash from explosive eruptions The pyroclastic material forms steep slopes

24 Composite Volcanoes Typically thousands of feet high & steep slopes Form from explosive eruptions of pyroclastic flows followed by quieter flows of lava This makes alternating layers of ash and lava Types of Volcanoes Video

25 Other Volcanic Features There are 3 other types of volcanic Landforms: Craters Calderas Lava Plateaus

26 Craters Crater = A funnel-shaped pit at the top of a volcano During eruptions, lava and pyroclastic flows build up material around the central vent If lava hardens in the center, the next eruption may blast it away. In this way, a crater becomes larger & deeper Volcano Crater Video

27 Calderas Caldera = Large circular depression of land above a magma chamber Forms when a magma chamber empties and the land above it sinks downwards The Yellowstone Caldera is 45 miles wide Caldera Formation Video Aniakchak Caldera, Alaska

28 Lava Plateaus Most lava comes (not from volcanoes but) from lava plateaus Lava Plateaus are landforms created by repeated eruptions from long cracks in Earth s crust The Columbia River Plateau formed between 14 & 17 million years ago in the North West U.S. Some places are 2 miles high

29 Volcanic Lightning! Caused when positively charged ejecta from volcanoes are separated from the negatively charged ground How Lightning Works Video Awesome Volcano Lightning Pictures Volcanic Lightning Video