THE EARTH’SCRUST

WHAT DO YOU MEAN BY CRUST..??

O In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle. 

HOW MANY TYPES OF CRUST ARE THERE..??

O The crust is divided into two types: oceanic crust and continental crust. Oceanic crust, found under the ocean floor, is made of dense rocks such as basalt. It is about 7 kilometres (4 miles) thick. Continental crust, found under land masses, is made of less dense rocks such as granite. Its thickness varies between 10 and 75 kilometres (6 to 47 miles).

WHAT IS THE EARTH’S CRUST MADE UP OF..??

O Earth's crust is made up of several elements: iron, 32 percent; oxygen, 30 percent; silicon, 15 percent; magnesium, 14 percent; sulphur, 3 percent; nickel, 2 percent; and trace amounts of calcium, aluminium and other elements.

O The crust is divided into huge plates that float on the mantle, the next layer. The plates are constantly in motion; they move at about the same rate as fingernails grow. Earthquakes occur when these plates grind against each other. Mountains form when the plates collide and deep trenches form when one plate slides under another plate. Plate tectonics is the theory explaining the motion of these plates.

OTYPES OF ROCKS IN THE EARTH’S CRUST

IGNEOUS ROCKSO Igneous rock (derived from the Latin word ignis meaning

fire) is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallization, either below the surface as intrusive(plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of Earth's crust.

Sedimentary rocksO Sedimentary rocks are types of rock that are

formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles (detritus) to settle and accumulate or minerals to precipitate from a solution Particles that form a sedimentary rock by accumulating are called sediment. Before being deposited, sediment was formed by weathering and erosion in a source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers which are called agents of denudation.

Metamorphic rocksO Metamorphic rocks arise from the

transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (1500 bars),causing profound physical and/or chemical change. The protolith may be sedimentary rock, igneous rock or another older metamorphic rock

HydrosphereO The hydrosphere (from Greek ὕδωρ

-hydōr, "water" and σφαῖρα - sphaira, "sphere”) in physical geography describes the combined mass of water found on, under, and over the surface of a planet.

wave O In physics, a wave is disturbance or oscillation

that travels through matter or space, accompanied by a transfer of energy. Wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass transport. They consist, instead, of oscillations or vibrations around almost fixed locations. Waves are described by a wave equation which sets out how the disturbance proceeds over time. The mathematical form of this equation varies depending on the type of wave.

TidesO Tides are the rise and fall of sea

levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.

Ocean CurrentsO An ocean current is a continuous, directed movement of seawater generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences, with tides caused by the gravitational pull of the Moon and the Sun. Depth contours, shoreline configurations and interaction with other currents influence a current's direction and strength.

Atmosphere Of EarthO The atmosphere of Earth is a layer

of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).

STRUCTURE OF THE ATMOSPHERE

TroposphereO The troposphere is the lowest portion of Earth's

atmosphere. It contains approximately 80% of theatmosphere's mass and 99% of its water vapour and aerosols. The average depth of the troposphere is approximately 17 km (11 mi) in the middle latitudes. It is deeper in the tropics, up to 20 km (12 mi), and shallower near the polar regions, approximately 7 km (4.3 mi) in winter. The lowest part of the troposphere, where friction with the Earth's surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred metres to 2 km (1.2 mi) deep depending on the landform and time of day. The border between the troposphere and stratosphere, called the tropopause, is a temperature inversion.

StratosphereO The stratosphere /ˈstrætəsfɪər is the second major layer

of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler higher up and warmer farther down. The border of the troposphere and stratosphere, the tropopause, is marked by where this inversion begins, which in terms of atmospheric thermodynamics is the equilibrium level. At moderate latitudes the stratosphere is situated between about 10–13 km (33,000–43,000 ft; 6.2–8.1 mi) and 50 km (160,000 ft; 31 mi) altitude above the surface, while at the poles it starts at about 8 km (26,000 ft; 5.0 mi) altitude, and near the equator it may start at altitudes as high as 18 km (59,000 ft; 11 mi).

MesosphereO The mesosphere (/ˈmɛsoʊsfɪər;

from Greek mesos "middle" andsphaira "ball") is the layer of the Earth's atmosphere that is directly above the stratopause and directly below the mesopause. In the mesosphere temperature decreases with increasing height. The upper boundary of the mesosphere is the mesopause, which can be the coldest naturally occurring place on Earth with temperatures below 130 K (−226 °F; −143 °C). The exact upper and lower boundaries of the mesosphere vary with latitude and with season, but the lower boundary of the mesosphere is usually located at heights of about 50 kilometres (160,000 ft; 31 mi) above the Earth's surface and the mesopause is usually at heights near 100 kilometres (62 mi), except at middle and high latitudes in summer where it descends to heights of about 85 kilometres (53 mi).

Thermosphere O The thermosphere is the layer of the Earth's atmosphere

directly above the mesosphere and directly below the exosphere. Within this layer, ultraviolet radiation (UV) causes ionization. Called from the Greek θερμός (pronounced thermos) meaning heat, the thermosphere begins about 85 kilometres (53 mi) above the Earth. At these high altitudes, the residual atmospheric gases sort into strata according to molecular mass (see turbosphere). Thermospheric temperatures i ncrease with altitude due to absorption of highly energetic solar radiation. Temperatures are highly dependent on solar activity, and can rise to 2,000 °C (3,630 °F). Radiation causes the atmosphere particles in this layer to become electrically charged enabling radio wavesto bounce off and be received beyond the horizon. In the exosphere, beginning at 500 to 1,000 kilometres (310 to 620 mi) above the Earth's surface, the atmosphere turns into space.

ExosphereO The exosphere (Ancient Greek: ἔξω éxō "outside

, external, beyond", Ancient Greek: σφαῖρα sphaĩra"sphere") is a thin, atmosphere-like volume surrounding a planetary body where molecules are gravitationally bound to that body, but where the density is too low for them to behave as a gas by colliding with each other. In the case of bodies with substantial atmospheres, such as the Earth's atmosphere, the exosphere is the uppermost layer, where the atmosphere thins out and merges with interplanetary space. It is located directly above the thermosphere.

 BiosphereO he biosphere is the global sum of all ecosystems. It

can also be termed the zone of life on Earth, a closed system (apart from solar and cosmic radiation and heat from the interior of the Earth), and largely self-regulating. By the most general biophysiological definition, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, geosphere, hydrosphere, and atmosphere. The biosphere is postulated to have evolved, beginning with a process of biopoesis (life created naturally from non-living matter such as simple organic compounds) or biogenesis (life created from living matter), at least some 3.5 billion years ago. The earliest evidences for life on Earth are graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in WesternGreenland and microbial matfossilsfound in 3.48 billion-year-old sandstone discovered inWestern Australia.

DONE BY MALHAR