Interior of the Earth 🌍

Source of information about the interior

The earth's radius is 6370 km.
Most of our knowledge about the interior of the earth is largely based on estimated and interference.

Direct sources

The most easily available solid Earth material is surface rock or the rocks we get from mining area.
Gold mines in South Africa are as deep as 3-4 kilometre. going beyond this depth is not possible as it is very hot at this Depth
Scientist have take taken on a number of project to penetrate Deeper to explore the conditions in the crustal portion.
Scientist word built over are working on to measure project such as deep ocean drilling project and integrated Ocean drilling project.
The deepest drill at Kola in Arctic Ocean, has so far reached a depth of 12 kilometre.
Volcanic eruption forms another source of obtaining direct information.
When the molten material (Magma) is thrown onto the surface of the earth, during volcanic eruption it become available for laboratory analysis.

Indirect sources

Analysis of Properties of Matter indirectly provide information about the interior.
We known through the mining activity that in temperature and pressure increased with the increasing distance from the surface towards the interior in deeper deaths.
It is also known that the density of the material also increases with depth.
Another source of information are the meteor that at time reach the earth.
The material and the structure observed in the meteor and are similar to that of the Earth.
There are solid bodies developed out of materials same as, or similar to our planet.
The Other indirect sources include gravitation, magnetic field and seismic Activity.
The gravitational force is not the same at different latitude on the surface.
It is Greater near the poles and less at the equator this is because of the distance from the centre at the equator being greater than that at the pole .
The Great Value also different according to the mass of material .
The uneven distribution of mass of material within the earth influences this value.
The regarding of the gravity at different place is influenced by many other factors .
These regarding different from the expected values such a different differences is called gravity anomaly.
Gravity anomalies give us information about the distribution of mass of material in The crust of Earth.
Magnetic Sureys also provide information about the distribution of magnetic material is the Crystal portion, and thus, provide information about the distribution of material in this part.
Seismic activity is one of the most important source of information about the interior of the earth.

Earthquake

An earthquake in simple word is shaking of the earth.
It is a natural event.
It is caused due to release of energy which generates wave that travel in all directions.

Why does the Earth shake?

The release of energy occurs along a fault.
A fault is a sharp break in the crustal rocks.
Rocks along a fault tend to move in opposite direction .
The blocks get deformed and eventually, they slide past one another abruptly. this caused a release of energy and the energy wave travel in all directions.
The point where the energy is released is called the focus of an earthquake , alternatively, it is called the hypocenter.
The energy wave travelling in different direction reach the surface.
The point on the surface, nearest to the focus, is called epicenter.
It is the first one to experience the Waves.it is a point directly above the focus.

Earthquake waves

All natural earthquakes take place in the lithosphere.
The lithosphere refer to the portion of death up to 200 km from the surface of the earth.
An instrument called seismograph record the wave reaching the surface.
Are curve of earthquake waves recorded on the seisgraph is given in figure .
The curve shows three distinct section each representing different type of wave pattern .
Earthquake wave are basically of two types body waves and surface waves.
Body waves are generated due to the release of energy at the focus and move in all direction travelling through the body of the earth hence the name body waves .
The body waves interact with the surface Rock and generate new set of waves called surface waves .
These wave move along the surface the velocity of waves change as it travels through material with different densities.
The denser the material, the higher is the velocity .
Their direction also changed as they reflect or refract when coming across materials with different densities.

There are two type of body waves

They are called p and S waves.

P-waves

P-waves move faster and are the first to arrive at the surface.
These are also called primary wave.
The P waves are similar to sound waves travel through gases, liquid and solid materials.

S-waves

S waves arrive at the surface with sometimelag.
These are called secondary waves.
Important fact about S waves is that they can travel only through solid materials.this characteristics of the S wave is quite important .
lt has helped scientist to understand the structure of the interior of the earth .
Reflection causes wave to rebound where is refraction makes wave move in different directions.
The variation in the direction of wave are inferred with the help of their record on seismograph.
The surface wave are the last two report on seismograph .
These waves are more destructive.
They causes displacement of Rock, and hence the collapse of structure occur.

Propagation of earthquake waves

Different type of earthquake waves travel in different manner.
P waves vibrate parallel to the direction of the wave .this exert pressure on the material in the direction of the propagation.
Other three waves vibrate perpendicular to the direction of the propagation.
The direction of the vibration of a S-wave is perpendicular to the wave direction in the vertical plane .hence they create troughs and crests in material through which they pass .
Surface waves are considered to be the most damaging waves.

Emergency of shadow zone

Earthquake waves get recorded in graphs located at power of locations .
There exist some specific area where the waves are not reported such as zone is called the shadow zone.
It was observed that has seismograph located at any distance within 105 degree from the epicenter, recorded the arrival of both p and S waves.
The seismograph located by on 145 degree from epicenter recorded the arrival of P waves but not that of s waves Ozone between 105 degree and 145 degree from centre was identified as the shadow zone for both the types of wave.
The entire beyond 105 degree does not receive S waves.
The shadow zone of s waves is much larger than that of the p waves.
The shadow zone of P waves appear as a band around the sun between 105 degree and 145 degree away from the epicenter .
The shadow zone of s waves is not only larger in extend but it is also little over 40 percent of the Earth surface.

Types of earthquakes

The most common ones are the tectonic earthquake these are generated due to sliding of rocks along a fault plane.
A special class of tectonic earthquake is sometimes recognised as volcanic earthquake however these are confined areas of active volcanoes.
In the areas of intense mining activities sometimes the roof of underground mines collapse causing minor tremors these are called collapse earthquake.
Ground shaking may also occur due to the explosion of chemical or nuclear device such tremors called explosion earthquakes.
The earthquakes that occur in the areas of large Reservoirs are referred to as a Reservoir induced earthquakes.

Measuring earthquakes

The earthquake events are scaled either according to the magnitude for density of the shock.
The magnitude scale is known as the Richter scale.
The magnitude relates to the energy released during the quake .
The magnitude is expressed in numbers 0-10 .
The density scale is named after Mercalli, an Italian seismologist .
The intensity scale takes into account the visible damage caused by the event .
The range of intensity scale is from 1-12.

Effects of earthquake

Earthquake is a natural hazard.

The following are the immediate hazardous effect of earthquake:

Ground shaking
Differentiation ground settlement
Land and mud slides
Soil liquefaction
Ground lurching
Avalanches
Ground displacement
Flood from dam and levee failure
Fires
Structural collapse
Falling objects
Tsunami

The first 6 listed above have some bearings upon landforms, while others may be considered the effects causing immediate concern to the life and properties of people in the region.
The effect of Tsunami would occur only if the epicenter of the tremor is below Oceanic waters and the magnitude is sufficiently high.
Tsunamis are waves sufficient generated by the tremors and not an earthquake in itself .
Through the actual quick activity lasted for a few seconds its effects are diverse stating provided the magnitude of the quake is more than 5 on the Richter scale.

Frequency of earthquake occurrence

The earthquake is a natural hazard.
If they are of high magnitude take place, it can cause heavy damage to the life and property of people.

The crust

It is the outermost solid part of the earth .
It is brittle in nature .
The thickness of the he crust varies under the oceanic and continental areas .
Oceanic crust it is thinner as compared to the continental crust.
The main thickness of oceanic crust is 5 km where is that of the continental is around 30 km .
The continental crust is thicker in the area of major mountain system it is as much as 70 km thick in the Himalayan region .
It is made up of heavier Rock having density of 3 gram per centimetre cube this type of rock found in OceanOctober crust is basalt . The mean density of material in Ocean across is 2.7 gram per centimetre cube.

The mantle

The portion of the interior beyond the crust is called the mantle.
The mantle extends from Moho 's discontinuity to the depth of 2900 km.
The upper portion of the Mantle is called asthnospere the word astheno means week.
It is considered to be extending up to 400 km .
It has a density higher than the crust (3.4 gram per centimetre cube ).
The crust and the upper most part of the Mantle are called lithosphere. its thickness range from 10 to 200 km.
The lower Mantle extend beyond the asthenosphere .it is in solid state.

The core

The earthquake waves velocities helped in understanding the existence of the core of the earth.
The core mantal boundary is located at the depth of 2900 km .
The outer core is in liquid state while the inner core is in solid state .
The density of material at the Mantle core boundary is around 5 gram per centimetre cube and at the centre of the earth at 6300 kilometre the density value is around 13 gram per centimetre cube.
The core is made up of very heavy material mostly constituted by Nickel and iron .it is sometimes referred to as the nife layer.

Volcanoes and volcanic landforms

Volcano is a place where gases, ashes and/ or molten Rock material lava escape to the ground .
A volcano is called and active volcano if their materials and are being released or have been released out in the recent past .
The layer below the solid crust in mantle.
It has higher density than that of the crossed the mental contain a weaker zone called asthenosphere.
The material in the upper Mantle portion is called Magma .
Once it starts moving toward the crust or it.

Volcanoes

Volcanoes are classified on the basis of nature of eruption and the form developed at the surface.

Major types of volcanoes are as follows:

Shield volcanoes

Barring the basalt that flows the shield volcanoes are the largest of all the volcanoes on the earth .
The Hawaiian volcanoes are the most famous example .
The hese volcanoes are mostly made up of basalt, A type of lava that is is very fluid when erupted .
They become explosive if somehow water get into the vent : otherwise they are characterized by low explosivity.

Composite Volcanoes

These volcanoes are characterized by eruption of cooler and more viscous lavas than basalt.
These volcanoes often result in explosive eruptions . along with lava large quantities of pyroclastic material and Ashes find their way to the ground.
This material accumulate in the vicinity of the vent opening leading to the formation of layers, and this makes the Mounts appear as composite volcanoes.

Caldera

These are the most explosive of the earth volcanoes.
They are usually so explosive that when they erupt that tend to collapse on themselves rather than building any tall structure.
The collapsed depressions are called calderas.
Their explosiveness indicate that the Magma chamber supplying the Lava is not only used but is only in close vicinity.

Flood Basalt Provinces

These volcanoes out for highly fluid Lava that flows for long distance.
Some parts of the world are covered by thousands of square km of thick Basalt Lava flows.
There can be a series of flows with some flows attaining thickness of more than 50 metre.
The Deccan traps from India presently covering most of the Maharashtra plateau, are a much larger flood basalt province .
It is believed that initially the Trap formation covered a much larger area than the present.

Mid Ocean ridge volcanoes

These volcanoes occur in the ocean areas.
There is a system of mid-ocean ridges more than 70000 km long that stretches through all the ocean basin.
The central portion of this Ridge experiences frequent eruptions.

Volcanic landforms

Intrusive forms

Lava that is released during volcanic eruptions on cooling develops into igneous rocks.
The cooling may take place either on reaching the surface or also while the lava is still in the crustal portion.
Depending on the location of the cooling of Lava, igneous rocks are classified as Volcanic rocks and Platonic rocks in the Lava that cools within the crustal portions assumes different form. these forms are called intrusive forms.

Batholiths

A large body of magnet matic material that cools in the deeper depth of The crust develops in the form of large domes.
They appear on the surface only after the denudational process remove the overlying materials.
They cover large areas, and at times, assume depth that may be several kilometre. these are granitic bodies.
Batholiths are the cooled portion of Magma Chambers.

Lacoliths

These are large dome shaped intrusive bodies with a level base and connected by a pine like conduit from below.
It can be regarded as the localised source of Lava that finds its way to the surface.
The Karnataka plateau is spotted with domal Hills of granite rocks.
Most of these, now exfoliated, are example of Lacoliths or Batholiths.

Lapoith, phacolith and sills

In case it develops into a saucer shape, Concave to the sky body, it is called landlord.
A Wavy mass of intrusive Rock, at times, is found at the base of synclines or at the top of anticline is folded in igneous country .
Such wavy materials have a defined conduit to source beneath in the form of Magma chambers. these are called the Phacoliths.
The near horizontal bodies intrusive igneous rock are called sill or sheet, depending on the thickness of the material.
The thinner ones are called sheets whope the thick horizontal deposit are called sills.

Dykes

When the lava makes its way cracks and the fissure developed in the land , it solidfies almost perpendicular to the ground.
It get cooled in the same position to develop a wall like structure. such structures are called dykes.
These are the most commonly found interusive form in the Western Maharashtra area.

B.R.Foundation

Class -11 NCERT fundamental of physical geography, chapter-3