Chapter 12 Vocab mid-ocean ridge discontinuity rift valley shadow zone divergent boundary convergent boundary subduction transform boundary fault elastic rebound focus epicenter discontinuity shadow zone asthenosphere viscosity cinder cone volcano shield volcano composite volcano

Earth’s Internal Processes Chapter 12 Earth’s Internal Processes

IV. Volcanoes Review Vocabulary: Melting Point → temperature at which a solid begins to liquefy. B. Melted rock inside Earth is called magma. C. Magma is (more, less) dense than the surrounding rock. D. Volcano → a feature that forms when magma reaches the surface and builds up to form a mountain.

E. Magma that has erupted onto Earth's surface is called Lava. F E. Magma that has erupted onto Earth's surface is called Lava. F. Where do most eruptions occur? At hot spots and plate boundaries. G. Hot Spots → are places in the mantle where the temperature is high enough to form magma.

H. Eruptive Products: 1. Solids a H. Eruptive Products: 1. Solids a. Pyroclasts → all solid materials expelled by a volcano. b. The larger the size of a pyroclastic particle, the (farther, closer) the particle will fall to the volcano.

Lava Fragments (Pyroclastic Debris) Tephra – solid fragments resulting from an explosive (Felsic) eruption Dust – smallest fragments Ash – fine pieces and flakes Cinders – pea-sized material Blocks – hardened lava about the size of a baseball Bombs – liquid lava that hardens as it falls

2. Gases a. What gases do volcanoes release 2. Gases a. What gases do volcanoes release? Water vapor, carbon dioxide and sulfur dioxide b. How does acid rain form when a volcano erupts? When sulfurous gases from volcanoes mix with water vapor in the atmosphere, acid rain forms.

3. Liquids a. Viscosity → a fluid’s resistance to flow. b 3. Liquids a. Viscosity → a fluid’s resistance to flow. b. Basaltic magma: - (high, low) viscosity and flows easily. - contains (more, less) silica; produces (quiet, explosive) eruptions.

Lava … magma reaching the surface 3 types of lava 1. Pahoehoe – lava that has a twisted or ropey texture

c. Granitic magma: (is the opposite) - (high, low) viscosity; thick, chunky lava - contains (more, less) silica; produces (quiet, explosive) eruptions.

I. Most of Earth’s volcanoes are located along a plate boundary. 1 I. Most of Earth’s volcanoes are located along a plate boundary. 1. At a convergent boundary, one plate subducts and sinks under another plate. 2. At a divergent boundary, most of the activity is underwater along the mid-ocean ridge.

3. Hot Spot  areas in Earth’s mantle that are (cooler, hotter) than the surrounding area, forming melted rock that rises toward the crust. a. What is an example of a hot spot? Hawaiian Islands b. These islands are all in a line because: The Pacific Plate is moving over a stationary hot spot.

J. Types of Volcanoes 1. Cinder Cone Volcano  small, violently erupting volcano formed by accumulation of large pyroclastic materials around a vent. a. Granitic magma b. (Quiet, Explosive) eruptions c. Pyroclastic material piles up (close to, far from) the volcanic vent.

Cinder Cone Sunset Crater – Flagstaff, AZ

Cinder Cone Sunset Crater – Flagstaff, AZ

2. Shield Volcano  broad, flat volcano formed by layers of free-flowing, high-temperature, basaltic lava. a. Basaltic magma b. (Quiet, Explosive) eruptions c. Describe the shape: broad, flat d. Example: Hawaiian Islands

3. Composite Volcano  large volcano formed by alternating lava flows and violently erupting pyroclastic materials. a. Contain both basaltic and granitic magma. b. (Quiet, Explosive) eruptions c. Describe the shape: largest and tallest volcanoes d. Example: Mount Saint Helens, Mount Rainier

Mt. Hood

Project Updates Project is Due Jan. 24th. Each student is to complete their own project. (1 per student). Pictures are to be drawn/ sketched/ (Draw …) (Pictures from clip art will not receive full credit, may lose point (s) per picture.)

Volcano Definition - an opening in the Earth’s crust through which an eruption takes place Mt. Pinatubo - Philippines – June 1991

Composite Volcano September 16, 1980 May 18, 1980 Mt. St. Helens - WA

Composite Volcano Mt. Ranier – Tacoma, WA

Lava Fragments (Pyroclastic Debris) Tephra – solid fragments resulting from an explosive (Felsic) eruption Dust – smallest fragments Ash – fine pieces and flakes Cinders – pea-sized material Blocks – hardened lava about the size of a baseball Bombs – liquid lava that hardens as it falls

Caldera – summit depression due to a collapse from a violent eruption Crater Lake - Oregon

Lahar – volcanic mudflow of ash, mud, snow and anything else that gets in its way! Muddy River - Mt. St. Helens

Lahars from Mt. St. Helens

View east across Haleakala Crater, with young cinder cones in foreground Blocks of basalt ejected during explosive eruptions at Halema`uma`u in 1924 Photograph by S.R. Brantley on August 14, 1998

Mt. Baker

Mt. St. Helens

Mt. Adams

Mt. Hood

Mt. Shasta

Three Sisters

Mt. St. Helens

Mt. St. Helens – pyroclastic flow

Spirit Lake at Mt. St. Helens

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