These DAV Class 7 SST Notes and DAV Class 7 SST Chapter 3 Notes – The Surface and the Interior of the Earth hold significant importance as study material for students.
The Surface and the Interior of the Earth Class 7 DAV Notes
→ The planet earth appears to be a large round ball that shines bright and blue.
→ Our earth has a variety of landforms on its surface. These are huge mountains and deep valleys, vast stretches of plains and plateaues.
→ The highest point of the earth’s surface is Mount Everest in the Himalayas and the lowest point is the bottom of the Marina Trench in the Pacific Ocean.
→ We know little about the interior of the earth because deep down, the temperature of the earth is very high which does not allow us to dig deep. Our knowledge of earth’s interior is, therefore, based on indirect observations like earthquakes and volcanoes.
→ The earthquake is the shaking and trembling of the earth’s surface, caused by internal movements.
→ The earth’s interior is made up of three layers- crust, mantle and core. Crust is a thin layer covering the outside of the earth. The thickness of the crust differs from place to place. Beneath the crust lies the mantle which extends upto 2900 km in depth. The core is the innermost part of the earth.
→ Our earth is a treasure of rock materials. Rocks are found in different shapes, sizes and colours. There are variety of rocks found on the earth’s crust.
→ On the basis of their formation, rocks are classified into three groups- igneous, sedimentary and metamorphic rocks.
→ Igneous rocks are formed due to intensive heat and pressure where molten material called magma coines out and solidifies over the earth’s surface as lava. They are of two types- intrusive igneous rocks and extrusive igneous rocks.
→ Sedimentary rocks are layered and formed by the deposition of sediments. Sandstone, limestone, clay, chalk are some examples of sedimentary rocks.
→ The rocks that are originally igneous or sedimentary in nature, get changed in character and appearance due to the heat and pressure and are called matamorphic rocks.
→ Minerals are substances naturally present in the earth. The most common minerals occurring inside the earth are iron, silver, gold, mica, bauxite and lead. The common salt is also a mineral.
→ Minerals are identified on the basis of their colour, hardness and lustre.
→ Seismology : The science of the study of earthquake.
→ Earthquake : Shaking and trembling of the earth’s surface, caused by internal movements.
→ Crust: The thin solid layer covering the outside of earth.
→ Mantle : The very thick layer of rocks lying beneath the crust.
→ Core : The innermost part of earth.
→ Rock : A naturally occurring solid substance made up of a mixture of minerals.
→ Magma : Very hot liquid rock found below the earth’s surface.
→ Mineral : A homogenous, naturally occurring substance with a definable internal structure.
→ Geologist: A scientist who studies geology (study of the earth).
→ Mean sea level : The level of the ocean surface between the level of mean high tide and low tide.
→ Mineral : A solid inorganic substance of natural occurrence.
→ Seismic wave : A wave of energy generated by an earthquake or other earth vibrations that travel within the earth or along its surface.