Volcanoes

What is Inside a Volcano?• Magma chamber = molten rock deep underground

that feeds the volcano

• Conduit = large tubelike structure that carries magma to the vent

• Vent = Magma is released through vents during an eruption

What is Inside a Volcano?

VENT

CONDUIT

MAGMA CHAMBER

Types of Volcanic EruptionsNon-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 1Eruption Video 2Eruption Video 3

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

Types of Volcanic Eruptions

Mt. Saint Helens, Washington State 1980

Best Explosive Eruptions Video

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 (CO2) 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

The Types of Magma is ImportantSilica 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

The Types of Magma is ImportantSilica 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

What Erupts from a Volcano?• Lava

– Molten rock made up of a slush of crystals, liquids and bubbles

– Mostly Silicon, Oxygen, Aluminum and Iron

• 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

Lava Video

What’s the Difference Between Magma & lava?

• Magma = molten rock under the Earth

• Lava = molten rock above the Earth

• They are really the same thing, one is just above, the other is below

Viscosity of Lava• Viscosity = 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

Types of Lava

• There are 4 main types of Lava

Aa Pahoehoe Pillow Lava Blocky Lava“Ah Ah” “Pa ho ho”

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 VideoKilauea Volcano, Hawaii

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

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

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

Types of Pyroclastic Material

• There are 4 main types of Pyroclastic Material

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

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

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.

Volcanic Ash• Very fine ash can stay in the atmosphere for years

and travel around the planet by wind currents• Forms when gas in magma expands & the walls of

the bubbles explode into tiny glass slivers

– Ash makes up most of a pyroclastic flow

Effects of Volcanic Ash - Video

Types of Volcanoes

• There are 3 main types of Volcanoes:

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

– Largest of the three types of volcanoes

• Mauna Loa, in Hawaii is 4,000 feet above sea level

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

Composite Volcanoes• Typically thousands of feet high & steep slopes

• Cycle through periods of quiet and explosive eruptions

• Form from explosive eruptions of pyroclastic flows followed by quieter flows of lava

– This makes alternating layers of ash and lavaTypes of Volcanoes Video

Other Volcanic Features

• There are 3 other types of volcanic Landforms:

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

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

Aniakchak Caldera, Alaska

Caldera Formation Video

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

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