Miss Nelson

SCIENCE ~ CHAPTER 6

VOLCANOES

Volcanoes and Plate Tectonics

SECTION 1

What do you remember about plate tectonics?

What are the types of plate boundaries?

ANTICIPATORY SET

S 6.1–Plate tectonics accounts for important features of Earth’s surface and major geologic events.

S 6.1.e – Students know major geologic events, such as earthquakes, volcanic eruptions, and mountain building, result from plate motions

STANDARDS

Where are most of Earth’s volcanoes found?

How do hot spot volcanoes form?

THE BIG IDEA

Volcano – a weak spot in the crust where magma has come to the surface

Magma – the molten mixture of rock-forming substances, gases, and water from the mantle

Lava – liquid magma that reaches the surface; also, the rock formed when liquid lava hardens

KEY TERMS

Ring of Fire – Volcano belt that rims the Pacific Ocean

Island arc – a string of islands formed by the volcanoes along a deep-ocean trench

Hot spot – an area where magma from deep within the mantle melts through the crust above it

KEY TERMS

Read “Volcanoes and Plate Tectonics” on page 216 of your

textbook

VOLCANOES AND PLATE TECTONICS

Volcanoes occur in belts that extend across continents and oceans

One major volcanic belt is the Ring of FireFormed by the many volcanoes that rim the Pacific Ocean

VOLCANOES AND PLATE BOUNDARIES

Volcanic belts form along the boundaries of Earth’s plates

VOLCANOES AND PLATE BOUNDARIES

At plate boundaries, huge pieces of crust spread apart or collide

As a result, the crust often fractures, allowing magma to reach the surface

Most volcanoes form along spreading boundaries such as mid-ocean ridges and along colliding boundaries where subduction takes place

VOLCANOES AND PLATE BOUNDARIES

Volcanoes form along the mid-ocean ridgesWhich mark spreading boundaries

Volcanoes also form along spreading boundaries on land

SPREADING BOUNDARIES

Many volcanoes form near colliding boundaries where oceanic plates return to the mantle

Volcanoes may form where two oceanic plates collide OR where an oceanic plate collides with a continental plate

View the diagram on page 218 of your textbook

COLLIDING BOUNDARIES

Many volcanoes occur near boundaries where two oceanic plates collide

The resulting volcanoes create a string of islands called an island arc

The curve of the island arc mirrors the curve of its deep-ocean trench

COLLIDING BOUNDARIES

Volcanoes also occur where an oceanic plate is subducted beneath a continental plate

COLLIDING BOUNDARIES

Read Volcanoes and Plate Boundaries on pages 217-218 of

your textbook

VOLCANOES AND PLATE BOUNDARIES

A volcano forms above a hot spot when magma erupts through the crust and reaches the surface

HOT SPOT VOLCANOES

Some hot spot volcanoes lie in the middle of plates far from any plate boundaries

Other hot spots occur on or near plate boundaries

HOT SPOT VOLCANOES

A hot spot in the ocean floor can gradually form a series of volcanic mountains

Hot spots can also form under the continents

HOT SPOT VOLCANOES

Where are most volcanoes located?

What is a hot spot?

CHECK FOR UNDERSTANDING

Where are most volcanoes located?Most volcanoes are located at colliding and spreading plate boundaries.

What is a hot spot?A hot spot is an area where material rises from deep within the mantle and melts to form magma.

CHECK FOR UNDERSTANDING

How does a hot spot volcano form?

GUIDED PRACTICE

How does a hot spot volcano form?A hot spot volcano forms as, over time, lava flows to the surface and forms new rock. The layers of rock accumulate to form a volcano.

GUIDED PRACTICE

Complete Volcanoes 6-1 Independent Practice

INDEPENDENT PRACTICE