VOLCANOES CHAPTER 3

Background Information Have you ever seen a volcano? What was happening? Iceland at Night

Volcano A weak spot in the crust where molten material comes to the surface.

Where are they found? Ring of Fire text pgs. 89-91 A major volcanic belt formed by many volcanoes that rim the Pacific Ocean is known as the Ring of Fire.

Diverging Plate Boundaries SuBduction Zones Hot Spots Volcanoes occur at three places: Diverging Plate Boundaries SuBduction Zones Hot Spots

Divergent Boundaries can form volcanoes at the mid-ocean ridge Divergent Boundaries can form volcanoes at the mid-ocean ridge. Lava pours out of cracks in the ocean floor. Most volcanoes at the mid-ocean ridge do not rise above the ocean’s surface!

Many volcanoes form near converging plate boundaries where oceanic crust returns to the mantle. Slabs of oceanic crust sink through a deep ocean trench into the mantle, where it forms magma that rises back toward the surface.

Island Arc Volcanoes at boundaries where two oceanic plates collide create a curved string of islands called a(n) island arc. Three major island arcs include Japan, New Zealand, Indonesia, the Caribbean Islands, the Philippines and the Aleutian Islands.

The Andes Mountains in South America were formed as a collision… between a continental and an oceanic plate

Hot Spot An area where magma deep within the mantle melts through the crust like a blow torch. The Hawaiian Islands formed as the Pacific plate drifted over a hot spot.

Volcanic Eruption Text pgs. 97-99

Magma forms in the asthenosphere beneath the lithosphere under great pressure. Liquid magma rises until it reaches the surface or becomes trapped beneath layers of rock. A molten mixture of rock-forming substances, gases, and water from the mantle is called magma.

Volcanic Activity- A volcanic eruption is much like carbon dioxide dissolved in soda rushing out when the soda is opened. The gases dissolved in magma rush out carrying magma with them Text pgs. 93-94

Magma Chamber and Vent Text pgs. 94-95 All volcanoes share a pocket below the volcano where magma is collected and a crack to the surface.

Parts of a VOLCANO A lava flow is the area covered by lava as it pours out of a vent. A crater forms at the top of the volcano’s central vent. The pipe of a volcano is a vertical crack in the crust.. pipe Magma chamber

Magma text pages 96-97 Characteristics of Magma depend on… dissolved gases (bubbles out on surface) temperature (hotter – flows more fluidly) silica content (more - the thicker it is)

Rock Types- High in silica (affects color and thickness) Light-colored and slow (too sticky) Examples: Rhyolite (composition like granite) A Pumice – gas bubbles are trapped and cool quickly) Obsidian – forms when high-silica lava cools quickly Low in silica Dark colored and flows easily Basalt can sometimes form these six-sided columns seen below

Lava When magma reaches the surface. Aa Examples of lava types Text pg.97 Examples of lava types Aa

Pyroclastic Flow A type of explosive eruption that hurls out a mix of hot gases, ash, cinders, and effects of a bomb.

Dormant A volcano that is still and active and will awaken in the future.

Extinct A dead volcano that will no longer erupt. Volcano is declared extinct after 50- 100 years of no eruptions.

Geyser A fountain of water and steam that erupts from the ground. Water is heated by hot rocks near magma pockets. The geyser releases pressure from superheated water as it erupts. How geysers work

VOLCANIC LANDFORMS Text pgs. 103-107

Landforms from Volcanoes

Landforms from Lava and Ash “How do they get their names?” Cinder Cone Composite Shield

What kinds of lava are connected with volcano type?

Shield volcano They are usually form from many layers of lava. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt. They result from quiet eruptions. The Hawaiian Islands are shield volcanoes. It is a gently sloping mountain formed by repeated lava flows (6e)

Composite (Strato-) Volcano A volcano built up by many layers (strata) of hardened lava pumice and volcanic ash. Three examples of this type of volcano are Mt. Fuji, Mt. St. Helens, and Mt. Hood. Their eruptions can be both quiet or explosive. It is a mountain formed by lava flows alternating with explosive eruptions. (8b)

Cinder Cone A steep hill-like volcano that slopes steeply. It is a cone-shaped mountain formed from ash, cinders, and bombs.(7c)

Lava Plateau High, level area formed by repeated lava flows (9a) Columbia Plateau Instead of forming mountains, some eruptions of lava form high, level areas called lava plateaus. First, lava flows out of several long cracks. The thin, runny lava travels far before cooling and hardening. This process repeats itself over and over again forming a plateau. An example is the Columbia Plateau that covers parts of Washington, Oregon, and Idaho.

Caldera The huge hole left by the collapse of a volcanic mountain. (10d)

Soils from Lava and Ash When volcanic ash breaks down, it releases potassium and phosphorus, both of which are needed by plants.

Five Features formed by Magma Volcanic necks Dikes Sills Batholiths Dome mountains

Volcanic Neck It looks like a giant tooth stuck in the ground. Forms when magma hardens a volcano’s pipe.

Dikes, Sills, Batholiths A dike is when magma forces itself across rock layers while magma that squeezes between layers of rock is called a sill. Batholiths are a mass of rock that has been formed when a large body of magma cools inside the crust.

Dome Mountain- other smaller bodies of magma can create dome mountains which form with rising magma being blocked by horizontal layers of rock . The magma pushes the layers to bend upward into a dome shape. Eventually the rock above the dome wears away, leaving it exposed. One example is the Black Hills in South Dakota.

Monitoring Volcanoes Monitoring Volcanoes Weekly Report

Supervolcano FYI Yellowstone Supervolcano

Are you ready for the Movie? Supervolcano Trailer