Earth Movements: Endogenic Forces, Volcanoes, Earthquakes

• The lithosphere is divided into lithospheric plates.
• These plates move very slowly, only a few millimeters each year.
• The movement is due to the molten magma inside the earth moving in a circular manner.
• The movement of these plates results in changes to the surface.
• Earth movements are divided based on the forces that cause them.
• Endogenic forces act in the interior of the earth.
• Exogenic forces work on the surface of the earth.

Endogenic Forces

• Endogenic forces can cause sudden movements or slow movements.
• Sudden movements include earthquakes and volcanoes, which can cause mass destruction.

Volcanoes

• A volcano is a vent (opening) in the earth's crust.
• Molten material erupts suddenly through this opening.

Earthquakes

• Earthquakes are vibrations on the surface of the earth caused by the movement of lithospheric plates.
• The vibrations travel all around the earth.
• The focus is the place in the crust where the movement starts.
• The epicentre is the place on the surface above the focus.
• Vibrations travel outwards from the epicentre as waves.
• Greatest damage occurs closest to the epicentre.
• The strength of the earthquake decreases away from the centre.
• There are three types of earthquake waves: P waves or longitudinal waves, S waves or transverse waves, and L waves or surface waves.
• Earthquakes cannot be predicted but the impact can be minimised if we are prepared.
• Locally, some earthquake prediction methods include studying animal behaviour, such as fish becoming agitated and snakes surfacing.

Measuring Earthquakes

• An earthquake is measured using a seismograph.
• The magnitude of the earthquake is measured on the Richter scale.
• Magnitude 2.0 or less is felt only a little.
• Magnitude over 5.0 can cause damage from things falling.
• Magnitude 6.0 or higher is considered very strong.
• Magnitude 7.0 is classified as a major earthquake.

Earthquake Preparedness

• The safest places to take shelter during an earthquakes are under a kitchen counter, table, or desk, against an inside corner or wall.
• Stay away from fireplaces, areas around chimneys, and windows that shatter.
• People should spread awareness and face disasters confidently.

Major Landforms

• The landscape is continuously worn away by weathering and erosion.
• Weathering is the breaking up of rocks on the earth's surface.
• Erosion is the wearing away of the landscape by different agents such as water, wind, and ice.
• Eroded material is carried away or transported and eventually deposited.
• Erosion and deposition create different landforms on the surface of the earth.

Work of a River

• Running water in a river erodes the landscape.
• Waterfalls are formed when a river tumbles at a steep angle over hard rocks or down a steep valley side.
• As a river enters the plain, it twists and turns, forming large bends called meanders.
• Continuous erosion and deposition along the sides of the meander cause the ends to come closer.
• Over time, the meander loop cuts off from the river and forms a cut-off lake, also called an ox-bow lake.
• When a river overflows its banks, it leads to flooding and deposits layers of fine soil and sediments, forming a flat fertile floodplain.
• The raised banks are called levees.
• As the river approaches the sea, it breaks up into a number of streams called distributaries, becomes slow, and deposits its load.
• Each distributary forms its own mouth, with all mouths forming a delta.

Work of Sea Waves

• The erosion and deposition of the sea waves gives rise to coastal landforms.
• Sea caves are formed when waves continuously strike rocks, causing cracks to develop.
• Sea arches are formed when the roof of sea caves collapses.
• Stacks are formed when further erosion breaks the roof of sea arches, leaving only walls.
• Sea cliffs are steep rocky coasts rising almost vertically above sea water.
• Sea waves deposit sediments along the shores, forming beaches.

Work of Ice

• Glaciers, or "rivers of ice," erode the landscape by bulldozing soil and stones.
• Glaciers carve out deep hollows that fill up with water when the ice melts, forming lakes.
• Materials carried by glaciers, such as rocks, sand, and silt, are deposited as glacial moraines.

Work of Wind

• Wind is an active agent of erosion and deposition in deserts.
• Mushroom rocks are formed when winds erode the lower section of rocks more than the upper part.
• Sand dunes are low hill-like structures formed when wind transports and deposits sand.
• Loess is formed when fine and light sand is carried over long distances and deposited in large areas; large deposits are found in China.