Volcanoes: A Presentation

VOLCANOES

What is it a volcano? A volcano is like a chimney in the Earth’s crust (surface) where magma flows out.

Eruption In 1883, in Indonesia, a volcano called Krakatoa erupted at first.

Krakatoa

The life of a volcano The inside of the Earth is very hot, and some of the solid rock melts to form hot, liquid rock called magma. The hole of the volcano is called vent. When magma leaves the vent it becomes lava.

Inside a volcano Vent

Hard lava Magma

Magma chamber

The Earth

The theory called plate tectonics explains how volcanoes form. Some volcanoes form above a hot spot, which is a very hot place in the mantle.

A volcanic eruption Contents: gas, dust, water vapour, lava and ash Gas, dust and water vapour

Vent Magma

Lava

Magma chamber

Layers of lava and ash

Types of volcano Scientists put volcanoes into three groups: • An Active volcano is one that is erupting or will soon erupt. • A Dormant volcano is one that has not erupted for a long time. • An Extinct volcano is one that has not erupted for more than 10.000 years.

Volcanic landforms Are in many places in the world, in many different shapes and sizes. TYPES OF VOLCANOES: Fissure volcano, Shield volcano, Dome volcano, Ash-cinder volcano, Composite volcano and Caldera volcano.

Rocks and lava Volcanoes produce lava and rocks we find on the Earth’s Surface. Magma forms igneous rocks. These fragments are called tephra.

Types of tephra

Bomb

Ash

Lapilli

Dust

Liquid lava flows fast and form smooth folds that look like rope this is called pahoehoe. When slow, sticky lava gets hard, it forms rocks with sharp edges; it’s called aa. Sometimes lava forms long, thing strings like human hair this are called Pele’s hair.

Underwater volcanoes The floor of the ocean is similar to dry land. There are flat plains, mountain ridges, canyons and trenches in the ocean floor. There are more volcanoes under the ocean than on the land.

Living with volcanoes The minerals and chemicals in the lava and ash make soil fertile so it’s good for farming. Volcanoes also produce electricity. This electricity is called geothermal energy and the people use it.

Volcanologists Special scientists are called volcanologists. They study volcanoes in different ways. This helps to learn about the volcano’s history and to know what it is going to do. Volcanologist’s suit

Laura GARRIGA SAGALÉS Laia GONZÀLEZ TORNER 2on C.C.S.E.P. CURS: 2008-2009