Our Changing Earth - Long Answer Questions
The lithosphere is broken into a number of plates. These plates move around very slowly (a few mm each year) because of the movement of molten magma inside the earth.
Endogenic: Forces that act in the interior of the earth (Earthquakes, Volcanoes). Exogenic: Forces that work on the surface of the earth (Wind, River, Glaciers).
A vent (opening) in the earth's crust through which molten material erupts suddenly.
When the Lithospheric plates move, the surface of the earth vibrates. These vibrations are called earthquakes.
Focus: The place in the crust where the movement starts. Epicentre: The place on the surface above the focus.
P waves (longitudinal), S waves (transverse), L waves (surface). Surface waves cause the most damage.
By a machine called Seismograph. The magnitude is measured on the Richter scale. An earthquake of 2.0 is small, 5.0 is damaging, 7.0 is major.
A massive earthquake measuring 6.9 on Richter scale hit Bhuj (Gujarat) on 26 Jan 2001. Enormous destruction occurred.
The breaking up of the rocks on the earth's surface.
The wearing away of the landscape by different agents like water, wind, and ice.
As the river enters the plain, it twists and turns forming large bends known as meanders.
Due to continuous erosion and deposition along the sides of the meander, the loop comes closer. Eventually, the meander loop cuts off from the river and forms a cut-off lake called an ox-bow lake.
Raised banks formed by the deposition of sediments along the river banks during floods.
Triangular landmass formed at the mouth of a river where it splits into distributaries and deposits sediments.
Erosion by sea waves. Hollow caves = Sea Caves. Roof remains only = Sea Arches. Roof breaks, only walls remain = Stacks.
The material carried by the glacier (rocks, sand, soil) gets deposited, forming glacial moraines.
In deserts, winds erode the lower section of the rock more than the upper part, creating a shape like a mushroom (narrow base, wide top).
When wind blows, it lifts and transports sand. When it stops, the sand falls and gets deposited in low hill-like structures.
When grains of sand are very fine and light, wind can carry it over long distances. When deposited in large areas, it is called Loess (extensive in China).
When the river tumbles at steep angle over very hard rocks or down a steep valley side.
Our Changing Earth - Important Facts
Lithospheric plates move due to circular magma flow.
Endo means inside, Exo means outside.
Volcanoes are sudden movements.
Earthquakes are sudden movements.
Mountain building is a slow movement.
Seismograph measures earthquakes.
Richter scale measures magnitude.
Magnitude 6 is strong.
Magnitude 7 is major.
Focus is inside, Epicentre is outside.
Bhuj earthquake was 6.9 magnitude.
Fire is a secondary hazard of earthquakes.
Tsunamis are caused by underwater earthquakes.
Waterfall: Angel Falls (Venezuela) is highest (979m).
Niagara Falls is in North America.
Victoria Falls is in Africa.
River erodes the landscape.
Meanders are bends in river.
Ox-bow lakes are cut-off meanders.
Floodplains are very fertile.
Distributaries are branches near the mouth.
Delta is a collection of sediments at mouth.
Sea cliff is a steep rocky coast.
Beach is deposition of sediments by waves.
Glacier is a river of ice.
Glaciers carve deep hollows.
Mushroom rocks found in deserts.
Wind is an agent of erosion in deserts.
Sand dunes are shifting hills of sand.
Loess is fine sand deposit.
Large loess deposits found in China.
Earthquake prediction is not possible yet.
Safe spots during earthquake: under kitchen counter.
Stay away from glass/windows during quake.
Mount Etna is a volcano in Italy.
Ring of Fire is in Pacific Ocean.
Himalayas are young fold mountains.
Ganga-Brahmaputra delta is largest.
Amazon river forms no delta (estuary).
Sea arches break to form stacks.
Stacks erode to form stumps.
Erosion and Deposition create landforms.
Running water is a powerful agent.
Ice is a powerful agent.
Wind is a powerful agent.
Gravity aids erosion.
Mass wasting is movement of soil downhill.
Soil formation takes thousands of years.
Our Changing Earth - Important Dates/Terms
Bhuj Earthquake