Learn about earth|layers

                                   Learn about earth|layers

Keywords: Crust |Mantle|Core|Lithosphere|Asthenosphere|Mesospheric| Oceanic crust|

Continental crust|Mohorovicic|Gutenberg |Lehmandiscontinuation| 

Introduction:

It was very hot when the earth was formed about 4.6 billion(4.6x109) years ago. Earth's core temperature is 5430-9800 degrees Fahrenheit which is about the sun's surface. During early days it was melting, so denser and heavy substances sank towards the center core, while less dense and lighter materials came to the surface. The core has 80% iron, and the rest 20% is Nickle and some other metals. It may be a single iron crystal.

 

The average density of the surface material of the earth is 3.0 gm/cm3, the inner material of the earth is about 9.0 gm/cm3. And that of the earth is 5.515 gm/cm3.

Table of contents:

1.	Chemical a)      Crust b)      Mantle c)      Core
2.	Mechanical a)Lithosphere b) Asthenosphere c) Mesospheric mantle d) Core- outer and inner.
3.	Discontinuation a)      Mohorovicic b)      Gutenberg c)      Lehmann

Structure

In two broad headings, we can discuss the structure of the earth i :

1. Chemical and 2. Mechanical.

Chemical: 1. Crust –outer and lower

2. Mantle-upper, transitional, and lower.

3. Core- outer and inner.

Mechanical:1.Lithosphere

2. Asthenosphere

3. Mesospheric mantle

4. Core- outer and inner.

The crust is the earth's outermost layer and extends from 0-35 km. It is divided into –an outer layer that extends from 0-10 km and the lower layer extending from 10-35km.

The thin part of the crust is Oceanic crust It extends from 5-10 km, underlies the ocean basins. It is composed of dense materials.

Continental crust is the thick crust and extends from 10-35 km and is composed of dense materials.

The rocks present in this layer are of two types:

1.    Sial, and 2. Sima.

Many rocks in this layer are less than 100 million (1x108) years old. However, some rocks are 4.4 billion (4.4x109) years old, indicating that the earth is older than 4.4 billion years.

Under crust, the Mantle layer is present, from which it is separated by a narrow inconsistent zone of 5-10 km, known as Core Mantle Boundary (CMB). Two different events take place at this boundary:

1. Discontinuity of the seismic velocity, which is known as Moho (Monorovicic discontinuity)

2. Chemical discontinuity in oceanic crust, between 'ultramafic cumulates' and 'tectonized harzburgites.'

The mantle layer is present between the crust and core layers. It is separated from the crust by crust-mantle boundary and from the core layer by D-layer(D-double-prime). It extends up to 2890 km and has three layers:

The upper mantle is from 35 -600 km, the transitional mantle is from 600-670 km, and the lower is from 670-2890 km.

The mantle is a solid hot layer and flows over the outer core layer. The source of energy to produce these movements are -1. Heat leftover during earth formation and 2. radioactive decay of radioactive metals such as uranium and thorium. The upper mantle with the crust layer forms the' Lithosphere."

The innermost part of the earth is the core, occupying about 65% of the earth's diameter. It is divided into

1. Solid inner core with a radius of 1220 km comprises solid iron 80% and rest 20% of nickel and other elements. It occupies about 20% of the earth's surface. Inge Lehmann discovered the inner core.

2. Liquid outer core encircling the inner core, and its radius is about 3400 km.

The knowledge of the earth's interior is gained indirectly using seismic waves produced by earthquakes, and it is based on observations of:

1. Topography

2. Bathymetry

3. Rocks present on the earth, and

4. Samples brought up to the surface by volcanoes.

The core does not allow these waves to pass through it.

In different layers of the earth, the seismic waves travel at different speeds and produce discontinuations. Some well-known discontinuations are :

1. The Mohorovicic discontinuation is produced between the crust and core layers.

2. The Gutenberg discontinuation is produced between the mantle and core layers.

3. The boundary between the inner and outer core produces Lehman discontinuation.

Hashtags: Crust#Mantle#Core#Lithosphere#Asthenosphere#Mesospheric# Oceanic crust#

Continental crust#|Mohorovicic#Gutenberg #Lehmandiscontinuation|# 

Outer crust     0-10 km	CMB↓	Moho discontinuation↓
Lower crust   10-35 km
Upper mantle 35-600 km	↓D line	Gutenberg discontinuation↓
Transition     600-670 km
Lower mantle 670- 3890 km
Outer core  3890-5150 km		Lehmann discontinuation↓
Inner core   5150-6370 km