7 Geography Chapter 3 Our Changing Earth

Chapter Notes and Summary
• Lithosphere is broken up into several plates, known as lithospheric plates.
• These plates move around very slowly. movement of these plates causes changes on surface of earth.
• These movements are divided on basis of forces which cause them.
• forces which act in interior of earth are called as Endogenic forces and forces that work on surface of earth are called as Exogenic forces.
• Endogenic force causes earthquakes and volcanic eruptions.
• Exogenic force causes weathering, erosion, deposition and gradation.
• Earthquakes are sudden vibrations inside earth’s crust.
• place in crust where movement starts is known as focus. epicentre of earthquake is place on surface above focus.
• It is measured by seismograph and intensity is measured by Richter scale.
• Weathering is breaking up of rocks on earth’s crust.
• Erosion is breaking away of landscape by different agents like water, wind and ice.
• Large bends formed by twisting and turning of river while entering plains are called meanders.
• An ox-bow lake is a cut–off lake formed due to cut–off of a meander loop.
• Wind is an active agent of erosion and deposition in deserts.

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