Volcanoes Chapter 9 Sections 1,2 and 3 VOLCANOES

A. What is a volcano? 1.An area of the Earth’s surface through which molten material, or magma, and volcanic gases pass. Magma- molten mixture of rock- forming substances, gases & water from the mantle Lava- Magma that reaches the surface 3. 75% of the volcanoes in the world are located in the Ring of Fire.

2. Most are located at plate boundaries % of the volcanoes in the world are located in the Ring of Fire. Ring of Fire

A circular pattern located around the pacific ocean along the plate boundaries where volcanoes are more common What is the Ring of Fire?

Where are volcanoes located? Volcanoes can be found: –Diverging Plate boundaries (mid-ocean ridge) –Converging plates with subduction zones Oceanic plate vs. oceanic plate Oceanic plate vs. continental plate –Hot spotsHot spots Area where magma from deep within the mantle melts through the crust like a blow torch –Example: Hawaiian IslandsHawaiian Islands

Eruptions Why do volcanoes erupt? Less dense magma seeps upward through cracks and creates volcanoes Gas in the magma is trapped and builds pressure Closer it gets to surface the less pressure it has and the gases separate (bubbles) Gases dissolve on the surface and magma is carried out Types of eruptions Quiet –lava moves steadily and easily Explosive – explodes and releases lave flow

Stages of a Volcano Active: (live) erupting or has shown signs that it may erupt In the near future Dormant: (Sleeping) is not currently erupting but may/can erupt in the future Extinct: (dead) unlikely to erupt again

3 Types of Volcanoes 3 Types of Volcanoes 1. Shield Volcano 2. Cinder Cone Volcano 3. Composite Volcano

Shield Volcano 1. Produced by: a. layers of lava released from non- explosive eruptions. b. lava spreads out over a wide area. c. created by hot spots 2. These volcanoes have: a. gently sloping sides. b. lava spreads out over a wide area. 3. Shaped like a shield Mount Kea, in Hawaii, is the largest volcano on Earth. Measured from its base on the sea-floor, it is taller than mount Everest.

Shield Volcano Here are 4 of the volcanoes that comprise the big island of Hawai'i. They are Mauna Kea (MK), Mauna Loa (ML), Hualalai (H), and Kohala (K). The photo was taken from near the summit of East Maui volcano (EM). These are the largest volcanoes on Earth.

Shield Volcano Belknap Shield Volcano in Oregon.

Cinder Cone Volcanoes 1.Produced from: a. moderately explosive eruptions. 2. Cinder cone volcanoes: a. have steep slopes. b. are usually small. c. often occur in clusters. d. cone – shaped hill/mountain

Cinder Cone Volcano Veniaminof, AlaskaMount Etna, Italy

1. Composite Volcanoes a. form from alternating explosive and non- explosive eruptions. b. broad bases and sides that get steeper toward the top. c. most common d. alternating layers of ash and lava Composite Volcanoes

Mount Ranier, Washington

Costa Rica- Arenal Volcano

F. What is a crater? 1.The area around the central vent of a volcano is called a crater.

More pics of Crater Lake:

What is a Hotspot? 1.an area of persistent volcanic activity. 2. originate at unusually hot areas of the mantle- core boundary. 3. Overlying mantle melts forming plumes of magma that rise and penetrate the crust forming volcanoes. 4. Hawaii, Iceland, and Yellowstone are examples of hot spots.