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Most of the knowledge we have about Earth’s deep interior comes from the fact that seismic waves penetrate the Earth and are recorded on the other side. Earthquake ray paths and arrival times are more complex than illustrated in the animations, because velocity in the Earth does not simply increase with depth. Velocities generally increase downward, according to Snell’s Law, bending rays away from the vertical between layers on their downward journey; velocity generally decreases upward in layers, so that rays bend toward the vertical as they travel out of the Earth . Snell’s Law also dictates that rays bend abruptly inward at the mantle/outercore boundary (sharp velocity decrease in the liquid) and outward at the outer core/inner core boundary (sharp velocity increase).
Major Points to remember about P S and Love waves
- P wave or primary wave. This is the fastest kind of seismic wave, and, consequently, the first to ‘arrive’ at a seismic station.
- The P wave can move through solid rock and fluids, like water or the liquid layers of the earth.
- P waves are also known as compressional waves.
- S waveor secondary wave, which is the second wave you feel in an earthquake. An S wave is slower than a P wave and can only move through solid rock, not through any liquid medium.
- Travelling only through the crust, Surface Wavesare of a lower frequency than body waves, and are easily distinguished on a seismogram as a result.
Earth’s Layers – Earth’s Composition
The Crust of Earth
It is the outermost and the thinnest layer of the earth’s surface, about 8 to 40 km thick. The crust varies greatly in thickness and composition – as small as 5 km thick in some places beneath the Oceans, while under some mountain ranges it extends up to 70 km in depth.
The crust is made up of two layers an upper lighter layer called the Sial (Silicate + Aluminium) and a lower density layer called Sima (Silicate + Magnesium).The Average density of this layer is 3 gm/cc.
The Mantle of Earth
This layer extends up to a depth of 2900 km.
Mantle is made up of 2 parts: Upper Mantle or Asthenosphere (up to about 500 km) and Lower Mantle. Asthenosphere is in a semimolten plastic state, and it is thought that this enables the lithosphere to move about it. Within the asthenosphere, the velocity of seismic waves is considerably reduced (Called ‘Low Velocity
The line of separation between the mantle and the crust is known as Mohoviricic Discontinuity.
The Core of Earth
Beyond a depth of 2900 km lies the core of the earth.The outer core is 2100 km thick and is in molten form due to excessive heat out there. Inner core is 1370 km thick and is in plasticform due to the combined factors of excessive heat and pressure. It is made up of iron and nickel (Nife) and is responsible for earth’s Magnetism. This layer has the maximum specific gravity.The temperatures in the earth’s core lie between 2200°c and 2750°c. The line of separation between the mantle and the core is called GutenbergWiechert Discontinuity.
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The Earth is a dynamic planet with a complex interior. The interior of the Earth is divided into four main layers: the crust, the mantle, the outer core, and the inner core.
The crust is the outermost layer of the Earth. It is made up of solid rock and is relatively thin, ranging from about 5 to 70 kilometers thick. The crust is divided into two types: continental crust and oceanic crust. Continental crust is thicker and less dense than oceanic crust. It is made up of rocks that are rich in silicon and aluminum. Oceanic crust is thinner and denser than continental crust. It is made up of rocks that are rich in magnesium and iron.
The mantle is the layer between the crust and the outer core. It is made up of solid rock and is much thicker than the crust, ranging from about 2,900 to 6,000 kilometers thick. The mantle is divided into two parts: the upper mantle and the lower mantle. The upper mantle is made up of rocks that are rich in magnesium and iron. The lower mantle is made up of rocks that are rich in silicon and Oxygen.
The outer core is the liquid layer between the mantle and the inner core. It is made up of molten iron and nickel. The outer core is much hotter than the mantle, ranging from about 4,000 to 6,000 degrees Celsius. The outer core is responsible for the Earth’s Magnetic Field.
The inner core is the solid layer at the center of the Earth. It is made up of solid iron and nickel. The inner core is much hotter than the outer core, ranging from about 5,000 to 6,000 degrees Celsius. The inner core is under so much pressure that it is solid, even though it is much hotter than the melting point of iron.
The Earth’s interior is constantly moving. The mantle is made up of solid rock, but it is very hot and under a lot of pressure. This causes the rock to move in a process called convection. Convection is the movement of heat through a fluid. In the case of the Earth’s mantle, the heat is coming from the Earth’s core. The hot rock rises to the surface, while the cooler rock sinks to the bottom. This movement of the mantle causes the plates of the Earth’s crust to move.
The Earth’s magnetic field is generated by the movement of the molten iron in the outer core. The Earth’s magnetic field protects us from harmful radiation from the sun and other sources. It also helps to guide birds and other animals during Migration.
The Earth’s interior is a fascinating and complex place. It is constantly moving and changing, and it is responsible for many of the Earth’s most important features, such as the magnetic field and the plates of the Earth’s crust.
Here are some frequently asked questions and short answers about the following topics:
The universe
What is the universe?
The universe is everything that exists, from the smallest subatomic particles to the largest galaxies. It is expanding at an accelerating rate, and it is thought to have begun with the Big Bang about 13.8 billion years ago.How big is the universe?
The observable universe is about 93 billion Light-years in diameter. This means that if you could travel at the speed of light, it would take you 93 billion years to travel from one side of the observable universe to the other.What is the age of the universe?
The universe is thought to be about 13.8 billion years old. This is based on measurements of the expansion of the universe and the cosmic microwave background radiation.What is the fate of the universe?
The fate of the universe depends on its density. If the density of the universe is high enough, gravity will eventually cause the universe to collapse back in on itself. If the density of the universe is low enough, the universe will continue to expand forever.What is The Solar System?
The solar system is the system of planets and other objects that orbit the Sun. It includes the Sun, eight planets, five dwarf planets, and hundreds of thousands of asteroids, comets, and meteoroids.What are the planets in the solar system?
The planets in the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Mercury is the closest planet to the Sun, and Neptune is the farthest.What are the dwarf planets in the solar system?
The dwarf planets in the solar system are Pluto, Eris, Makemake, and Haumea. Pluto was originally classified as a planet, but it was reclassified as a dwarf planet in 2006.What are the moons in the solar system?
There are over 200 moons in the solar system. The largest moon is Ganymede, which is larger than the planet Mercury.The Earth
What is the Earth?
The Earth is the third planet from the Sun and the only planet in the solar system known to support life. It is a terrestrial planet with a solid surface.What is the Atmosphere of the Earth?
The atmosphere of the Earth is a layer of gases that surrounds the planet. It is made up of nitrogen (78%), oxygen (21%), argon (0.9%), and other gases.What is the surface of the Earth?
The surface of the Earth is divided into land and water. The land is made up of continents and islands, and the water is made up of oceans, seas, and lakes.Life on Earth
What is life?
Life is a complex system that is capable of self-replication and self-maintenance. It is found on Earth in many different forms, including Plants, animals, and bacteria.How did life on Earth begin?
The origin of life on Earth is a mystery that scientists are still trying to solve. There are many theories about how life began, but no one knows for sure.What are the different types of life on Earth?
There are millions of different species of life on Earth. They can be divided into two main groups: plants and animals. Plants are photosynthetic, which means they can make their own food using sunlight. Animals are heterotrophic, which means they must eat other organisms to survive.The future of Earth
What is the future of Earth?
The future of Earth is uncertain. It depends on many factors, including human activity, Climate change, and natural disasters.What can we do to protect Earth?
There are many things we can do to protect Earth. We can reduce our carbon emissions, conserve energy, and recycle. We can also support organizations that are working to protect the Environment.
Sure, here are some MCQs without mentioning the topic Interior of earth:
The Earth’s core is made up of two parts: the inner core and the outer core. The inner core is solid and made up of iron and nickel. The outer core is liquid and made up of iron and nickel.
The Earth’s mantle is the layer between the crust and the core. It is made up of solid rock and is about 2,900 kilometers thick.
The Earth’s crust is the outermost layer of the Earth. It is made up of solid rock and is about 10-70 kilometers thick.
The Earth’s atmosphere is the layer of gases that surrounds the Earth. It is about 100 kilometers thick and is made up of nitrogen, oxygen, argon, and other gases.
The Earth’s oceans cover about 71% of the Earth’s surface. They are made up of salt water and are about 4,000 meters deep on average.
The Earth’s magnetic field protects the Earth from harmful radiation from the sun. It is generated by the movement of molten iron in the Earth’s outer core.
The Earth’s rotation causes the day and night cycle. It takes the Earth 24 hours to rotate once on its axis.
The Earth’s orbit around the sun causes the seasons. It takes the Earth 365.25 days to orbit the sun once.
The Earth’s tilt causes the seasons to be more extreme in the Northern Hemisphere than in the Southern Hemisphere. The Earth’s axis is tilted at an angle of 23.5 degrees relative to its orbital plane.
The Earth’s gravity pulls objects towards its center. The force of gravity is stronger at the Earth’s surface than it is at higher altitudes.
The Earth’s atmosphere is thicker at the equator than it is at the poles. This is because the Earth’s rotation causes the atmosphere to bulge out at the equator.
The Earth’s temperature is warmer at the equator than it is at the poles. This is because the Earth’s axis is tilted and the sun’s rays are more direct at the equator than they are at the poles.
The Earth’s landmasses are concentrated in the Northern Hemisphere. This is because the Earth’s crust is thicker in the Northern Hemisphere than it is in the Southern Hemisphere.
The Earth’s oceans are concentrated in the Southern Hemisphere. This is because the Earth’s crust is thinner in the Southern Hemisphere than it is in the Northern Hemisphere.
The Earth’s climate is changing. The average temperature of the Earth’s atmosphere has increased by about 1 degree Celsius since the late 19th century. This warming is caused by human activities, such as the burning of fossil fuels.
The Earth’s ice caps are melting. The Greenland ice sheet is melting at a rate of about 200 billion tons per year. The Antarctic ice sheet is melting at a rate of about 100 billion tons per year. This melting is causing sea levels to rise.
The Earth’s forests are being destroyed. About 15 billion trees are cut down each year. This deforestation is causing the Earth’s climate to change and is leading to the extinction of many species of plants and animals.
The Earth’s oceans are being polluted. About 8 million tons of plastic are dumped into the oceans each year. This pollution is killing marine life and is contaminating the seafood that we eat.
The Earth’s atmosphere is being polluted. About 9 billion tons of greenhouse gases are emitted into the atmosphere each year. These greenhouse gases are causing the Earth’s climate to change.
The Earth’s Resources are being depleted. We are using up the Earth’s resources at an unsustainable rate. This is leading to the depletion of fossil fuels, the destruction of forests, and the pollution of the oceans.
I hope these MCQs were helpful!