Geology: Lecture:no:10
Earth structure: The earth consists of several layers. The three main layers are the core, the mantle and the crust. The core is the inner part of the earth, the crust is the outer part and between them is the mantle.
Core: The inner part of the earth is the core. This part of the earth is about 1,800 miles (2,900 km) below the earth's surface. The core is a dense ball of the elements iron and nickel. It is divided into two layers, the inner core and the outer core. The inner core - the center of earth - is solid and outer core is so hot that the metal is always molten, but the inner core pressures are so great that it cannot melt.
Mantle: The layer above the core is the mantle. The mantle is to divide into the inner mantle and the outer mantle. The mantle is a part of a terrestrial planet. The mantle is a highly viscous layer between the crust and the outer core. Upper mantle is also called solid mantle and inner mantle is also called fluid mantle these names are due to their compositions.
Crust: In geology, a crust is the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle. The crust lays above the mantle and is the earth's hard outer shell, the surface on which we are living. In relation with the other layers the crust is much thinner. It floats upon the softer, denser mantle. The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks.
The earth's crust consists of a number of moving pieces or plates, that are always colliding or pulling apart.
Lithosphere:
The lithosphere is the rigid outermost shell of a rocky planet. It comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater.
In the Earth, the lithosphere includes the crust and the uppermost mantle, which constitute the hard and rigid outer layer of the Earth.
Plate tectonics:
The earth's crust consists of a number of moving pieces or plates, that are always colliding or pulling apart. The Lithosphere consists of nine large plates and twelve smaller ones. The continents are imbedded in continental plates; the oceanic plates make up much of the sea floor. The study of Tectonic plates - called plate tectonics - helps to explain continental drift, the spreading of the sea floor, volcanic eruptions and how mountains are formed.plate movement is due to interior heat and the slow churning of the mantle beneath them. Mantle rock is constantly moved upwards to the surface by the high temperatures below and then sinks by cooling.
Earth quakes:
An Earthquake is in fact the shaking of the ground caused by sudden movements in the earth's crust. The biggest earthquakes are set off by the movement of tectonic plates. Some plates slide past each other gently, but others can cause a heavy pressure on the rocks, so they finally crack and slide past each other. By this, vibrations or shock waves are caused, which go through the ground. It is these vibrations or seismic waves which cause an earthquake
Volcanoes:
A Volcano is a gap in the earth where molten rock and other materials come to the earth's surface. Some volcanoes are just cracks in the earth's crusts. Others are weak places in the earth's crust, which occur on places where magma bubbles up through the crust and comes to the earth's surface. Magma is molten rock that occurs by partial melting of the crust and the mantle by high temperatures deep down in the ground. Once magma comes to the earth's surface it is called lava.
Solar energy:
Energy coming from sun to earth in form of radiant light and heat is called solar energy.solar energy is maximum at tropical areas.
1. Tropic of Capricorn.
2. Tropic of cancer.
Meteorology:
Meteorology is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and short term forecasting.
Dust storm:
A dust storm or sandstorm is a meteorological phenomenon common in arid andsemi-arid regions. Dust storms arise when a gust front blows loose sand and dustfrom a dry surface. Particles are transported by saltation and suspension, causingsoil erosion from one place and deposition in another.
The term sandstorm is used most often in the context of desert sandstorms, especially in the Sahara, or places where sand is a more prevalent soil type than dirt or rock
Sand dunes:
Shapes of sand dunes:
Following are the different shapes of sand dunes due to wind processes.
1. Crescentic
2. Linear
3. Star
4. Dome
5. Parabolic
6. Longitudinal (Seif) and transverse dunes
7. Reversing dunes
Whirl wind:
A whirlwind is a weather phenomenon in which a vortex of wind (a vertically oriented rotating column of air) forms due to instabilities andturbulence created by heating and flow (current) gradients.
Cyclone:
In meteorology, a cyclone is an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds.
i-e Hurricane Katrina.
Tornado:
A tornado (often referred to as a twister or, erroneously, a cyclone) is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus or, in rare cases, the base of a cumulus cloud.
