Volcanoes Introduction and Review

Volcanoes: Videos Introduction to Volcanoes: VOzA VOzA What is a volcano? uLok uLok WY4 WY4

What is latitude? Longitude?

Latitude Latitude gives the position on Earth north or south of the equator – Positive north of the equator, negative south of the equator

Longitude Longitude gives the position on Earth east or west of the Prime Meridian – Positive east of the Prime Meridian, negative west of the Prime Meridian

Where on Earth are volcanoes located?

Volcanoes around the world

Plate boundaries

Most (but not all) volcanoes are located on plate boundaries.

What earth processes can create volcanoes? Animations

1. Subduction zones 2. Spreading centers 3. Hotspots Locations of Volcanoes Subduction happens when one tectonic plate dives beneath another. The plate drags water- rich sediments and oceanic crust down that release their water upon heating causing the overlying mantle rock to melt. These melts rise to the surface, and erupt to create volcanoes. Hotspots can occur in the middle of plate boundaries. A column of hot, buoyant mantle material rising and breaking through the crust to form a volcano forms the hotspots. As the plate moves, the column of mantle material stays in one place and the magma from the mantle must break through in another place in the crust. As the plate continues to move, a chain of volcanoes is formed. Most volcanic activity on earth occurs at spreading centers. This is the location where new crust is made. As the plates spread apart from one another, pressure is released on the mantle rock below, which makes it rise and then melt.

What are the three types of volcanoes? Shield volcanoes Stratovolcanoes Cinder cones Shield volcanoes Stratovolcanoes Cinder cones

Shield Volcano: A gently-sloped volcano.

Cinder Cone: A volcano made of cinders that are blown into the air.

Composite: A volcano built of alternating layers of cinders and lava.

What kind of volcano is this?

Mount Shasta is a composite volcano. Over the last 10,000 years, Mt. Shasta has erupted on average once every 800 years. During the 3,500 years the volcano has erupted about once every 300 years. The most recent eruption may have occurred in 1786 A.D.

What kind of volcano is this?

Diamond Head is an eroded Cinder (Tuff) Cone. Early sailors mistakenly thought glistening calcite crystals inside the tuff rocks were diamonds, leading to the incorrect name. Diamond Head formed when hot magma rising up a conduit hit ocean water, causing large explosions that threw exploded magma particles (tuff) into a broad ring.

What kind of volcano is this?

Kohala is a shield volcano. Kohala is the oldest of the subaerial volcanoes that make up the Island Of Hawaii. Kohala is considered to be extinct because it has not erupted for 60,000 years.

Relative sizes of volcanoes

Types of volcanoes 1. Shield volcanoes - Largest - Usually formed at hotspots 2. Stratovolcanoes - Most explosive - Usually formed at subduction zones 3. Cinder cones - Most common - Smallest - Usually formed at subduction zones - Short lived

Shield volcanoes: Mauna Loa and Mauna Kea

Shield volcano: Mt. Wrangell, Alaska

Stratovolcano: Mayon, Philippines

Stratovolcano: Mt. Rainier, Washington

Cinder cone: Barren Island, Andaman Islands

Cinder cone: Parícutin, Mexico

Key Points Latitude vs. Longitude Most volcanoes are located on plate boundaries Locations of volcanoes Subduction zones Spreading centers Hotspots Types of volcanoes Shield volcanoes Stratovolcanoes Cinder cones

Where does magma come from? The mantle!

Solid mantle rock can melt to form magma in either of these cases: 1.Decrease in pressure – Occurs at hotspots and spreading centers 2.Addition of water – Occurs at subduction zones

Anatomy of a Volcano

Intrusion vs. Extrusion Intrusion: When magma rises, reaches the crust, pushes into the crust, but cools and hardens beneath the surface. Extrusion: When magma pushes into the crust and erupts. – When magma reaches the surface and erupts, the magma changes its name to lava. – Volcanic eruption

Active volcano

Extinct volcano

Key Points Solid mantle rock can melt to form magma by: – A decrease in pressure – Addition of water – An increase in temperature Intrusion – magma – Pluton – Batholith – Dike – Sill Extrusion – lava – Magma chamber – Conduit – Vent