Tag: #structure

Structure of the Earth

 The earth’s interior is divided into three layers: crust, mantle, and core. The crust is the earth’s outermost layer, and the core is the earth’s innermost layer, located at a depth of 2900 kilometers. This article provides a brief overview of the earth’s three interior layers.

Core

The core is the source of the Earth’s internal heat. This is due to the presence of radioactive materials, which emit heat as they degrade into more stable materials. The core is located at the center of the Earth. It has two layers –
  • Inner core
  • Outer core

Inner Core – The inner core can reach temperatures of up to 4000°C, while the outer core can reach temperatures of up to 3600°C. The Lehmann Discontinuity is a liquid-solid boundary that exists between these two layers. This is the most intense part of the core. It’s as hot as the Sun’s surface!

The inner core is approximately 1216 km thick. It’s made of solid iron and nickel. These heavy metals would have sunk to the centre of the young Earth. The liquid outer core rotates around the solid inner core.

Outer Core – The outer core is approximately 2270 km thick. It’s made of liquid iron and nickel. Because it is under less pressure than the inner core, it is liquid. This layer is also electrically conductive. This produces the electrical currents that make up the Earth’s magnetic field.

Mantle

The mantle is located above the core. The mantle is composed of two layers of hot, dense, semi-solid rock. The mantle, like the core, has two layers – 

  • Lower Mantles
  • Upper Mantles

These are approximately 2885 km thick. This layer is so massive that it accounts for approximately 84% of the total volume of the Earth! The mantle’s temperature is lower than the core’s. It only gets to about 3000°C. The material becomes less dense as you move from the lower to upper mantle.

A transition zone exists between the lower and upper mantles. It is located 400-660 kilometers beneath the Earth’s surface.

The upper mantle is located above the transition zone. This zone extends from 400 km below the Earth’s surface to the crust layer. The asthenosphere is the uppermost part of the upper mantle. The asthenosphere is composed of fluid, soft rock.

Crust 

The crust is our planet’s solid, rigid outer layer. The crust is not a continuous layer of rocks, but consists of large masses called plates, which are free to drift slowly on top of the asthenosphere. It ranges in thickness from 5 to 80 km. The lithosphere is made up of the upper asthenosphere and the crust. 
The ocean floor contains the thinnest parts of the crust. It contributes to the formation of the oceanic crust. This section of the crust may be as thin as 5 km.
The continents contain the thickest parts of the Earth’s crust. It contributes to the formation of the continental crust. This layer of the crust can be up to 80 kilometers thick.
The crust closest to the mantle has a temperature of about 500°C. The temperature of the crust near the Earth’s surface is roughly the same as the temperature of the air.

PULSES- STRUCTURE, COMPOSITION AND PROCESSING

WHAT ARE PULSES?
Pulses are basically a fruit part of leguminous crops that are harvested solely for the seeds. Dried beans, lentils, and peas are the most common known and consumed pulses. Pulses do not include crops which are harvested green – these are the vegetable crops. Also excluded are those crops used mainly for oil extraction and leguminous crops that are exclusively used for sowing purposes.
Generally, all pulses have a similar structure, but differ in color, shape, size and thickness of the seed coat.
Mature seeds have three components – Seed Coat, Cotyledons and Embryo.
The seed coat or hull accounts for 7-15% of whole seed mass, cotyledons accounts for 85% of total seed and embryo for 1-4%.

STRUCTURE
The external structures of the seed are testa (i.e. seed coat), hilum, micropyle and raphe.
• The testa is the outer most part of the seed and covers almost all of the seed surface.
• The hilum is an oval scar on the seed coat where the seed was attached to the stalk.
• The micropyle is a small opening in the seed coat next to the hilum.
• The raphe is a ridge on the side of the hilum opposite to the micropyle.
When the seed coat is removed from the grain, the remaining part is the embryonic structure. The embryonic structure of the pulse consists of two cotyledons (or seed leaves) and a short axis above and below them These two cotyledons are not physically attach to each other except at the axis and a weak protection is provided by the seed coat to these cotyledons. Thus, the seed is usually vulnerable to breakage. The outermost layer of the seed coat is the cuticle, and it can be smooth or rough.
• Both the micropyle and the hilum are related to the permeability of the testa and to water absorption.

COMPOSITION
Carbohydrates – 55-65%
Proteins – 18-25%
Fat – 1-4%
Minerals – 1-3%
Fibers – 1-5%

PROCESSING OF PULSES

There are various steps involved in processing of pulses:

  1. SOAKING – Soaking in water is the first step in preparing pulses for consumption. It reduces the oligosaccharides of the raffinose family. It also reduces the amount of phytic acid in pulses.
  2. GERMINATION – It improves the nutritive value of food pulses. The ascorbic acid content of pulses increase manifold after 48 hours of germination. The germination process decreases or eliminates most of the anti nutritional and toxic factors in several pulses.
  3. DECORTICATION – It is a simple method to soak the seeds for a short time in water, the husk takes up more water than the seeds and may be easily separated by rubbing while still moist. In the alternative, the soaked grains may be dried and the husk is removed by pounding and winnowing. Roasting also renders the husk easier to separate.
  4. COOKING – It destroys the enzyme inhibitors and thus improves the nutritional quality of food pulses. It also improves the palatability of the pulse.
  5. FERMENTATION – This process increases the pulse digestibility, palatability and nutritive value. It also improves the availability of essential amino acids and thus, the nutritional quality of protein of the blend.
  6. PULSE MILLING – The removal of the outer husk and splitting the grain into two equal halves is known as milling of pulses.