Volcanoes 7

SUMMARY -Eruption! -The live of a volcano -Volcanic landforms -Underwater volcanoes -Living with volcanoes -Volcano words

VOLCANO • A volcano is like a chimney in the Earth’s crust (surface) where magma flows out. • The inside of the Earth is very hot, and some of the solid rocks melts to form hot liquid rock called magma. Eventually magma and ash break through a hole in the Earth’s surface. The hole is called a vent. • When magma leaves the vent, it becomes lava.

Parts of the volcano

Plate tectonics • Plate tectonics theory, explains how volcanoes form. • Some volcanoes form above a hot spot, which is a very hot place in the mantle. Plate movements Plates bumping Plates moving apart

Earth’s plates

Types of vocano 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 -Caldera volcano

Rocks and lava Volcanoes produce lava and rocks we find on the Earth’s surface. Magma forms igneous rocks. Fragments of igneous rocks sometimes erupt from a vent. These fragments are called tephra. TYPES OF TEPHRA -Bomb -Lapilli -ash -dust

Liquid lava flows fast and forms smooth folds that look like rope. This is called pahoehoe. When slow sticky lava gets hard, it forms rock with sharp edges, it’s called aa. Sometimes lava forms long, thin strings like human hair. These are called Pele’s Hair.

Unusual lava shapes Lava has created unusual shapes in many places.

Underwater volcanoes The floor of the ocean is similar to dry land. There are more volcanoes under the ocean than on land.

Living with volcanoes The minerals and chemicals of the lava and ash make the soil fertile so it is good for farming. Volcanoes also help to produce electricity. They heat rocks that are near the Earth’s crust. When these rocks heat underground water it turns to steam. People use this steam to make electricity. This is called geothermal energy.

A volcanic eruption Volcanoes erupt because pressure force magma to the surface. • Contents: gas, dust, water vapour, lava and ash. 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.

Volcanologists Special scientists are called volcanologists. Volcanologists study volcanoes in different ways. They study rocks and ash from long ago. Scientists must collect rocks, gases and lava to take back to the laboratory. When they visit volcanoes, they wear gas masks because the gases are poisonous.

The volcanologits wear gas masks because the gases are poisonous.

Andrea Pla i Maria Samper 6è primaria