The Ring of Fire is a ring of volcanoes around the Pacific Ocean. These volcanoes result from subduction of oceanic plates beneath lighter continental plates, A subduction zone is a place where one plate of oceanic lithosphere is shoved under another plate. As it is shoved into the hotter mantle the plate heats up. The addition of volatiles such as water to the hot overlying mantle causes partial melting and the production of magma. This magma rises up through the over-lying plate to erupt at the surface. Hence, the Pacific Ring of Fire is most seismically and volcanically active.

GPS works by sending radio signals from satellites to ground stations. The distance between the satellites and station is recorded. Over time, these distances change slightly. Scientists can measure the rate of Tectonic Plate movements by recording the time it takes for ground stations to move a given distance.

(i) The internal processes generate heat and eject materials from deep below the Earth's crust.
(ii) Internal radioactivity in the principal source of power for this process.

The science that deals with the physical structure and substances of the earth their history and the processes which act on them.

The Hydrosphere is the watery part of the Earth's surface including oceans, rivers, lakes and water vapour.

(i) Earthquakes are generally caused by the sudden vibrations in the Earth's crust.
(ii) It spreads outward in all directions from the Earth's crust.
(iii) The point of origin of an Earthquake is called 'Focus' which generates a series of elastic waves.
(iv) 'Epicentre' is a point on the Earth's surface that lies directly above the focus.
(v) The impact of the Earthquake is felt the most at the epicentre.

(i) The word 'Tsunami' is a Japanese term meaning harbour waves.
(ii) It is generated sea waves caused by Earthquakes, submarine explosions and landslides.
(iii) These waves travel more than 500 km per hour. These waves are called Tsunami.

The 'Pedosphere' is part of the lithosphere made up of soil and dirt. It exists at the interface of lithosphere, atmosphere, hydrosphere and biosphere.

(i) The Earth is a unique planet of the Solar family.
(ii) The Earth is composed of four spheres.
(iii) They are lithosphere, the atmosphere, the hydrosphere and the biosphere.
(iv) The four spheres of the Earth interact with one another.
(v) The abiotic spheres are the lithosphere, atmosphere and hydrosphere.
(v) The biotic sphere is the biosphere.

Constructive Effects: Volcanic materials enrich the soil fertility that promotes agricultural activities. The hot volcanic region helps in generating geothermal energy. Many dormant and active volcanoes are the most attractive tourist spots of the world. Most of the volcanic materials are used as building materials.
Destructive Effects: Volcanic eruption causes Earthquakes, fast floods, mudslide and rock fall. Lava can travel very far and burn, bury or damage anything in its path: The large amount of dust and ash makes breathing hard and irritable. Volcanic eruptions can alter the weather conditions and disrupt transport (Iceland volcanic eruption) in and around the volcanic region.

The outer surface and inner core of the Earth are totally different in their nature and structure. The structure of the Earth's interior is divided into three layers namely the crust, the mantle and the core.
Crust: Crust is the outer layer of the Earth, where we live. It is the skin of our Earth, which ranges between 5 to 30 km. It is the solid and rigid layer of the Earth. The thickness of the crust is greater below the continents than the ocean floor. The crust is classified as continental crust and oceanic crust. The major elements of crust are Silica (Si) and Aluminium (Al) and thus, it is termed as SIAL.
Mantle: The interior part beneath the crust is called mantle, which is about 2,900 km thick. The major elements of the mantle are Silica (Si) and Magnesium (Mg) and hence it is also termed as SIMA. In the upper part of the mantle. the rock remains solid, whereas, in the lower part of the mantle, rocks are in molten form. This molten rock inside the Earth is called 'magma'.
Core: The core is the innermost and hottest layer of the Earth which lies below the mantle. It is composed mainly of Nickel (Ni) and Iron (Fe). Hence it is called NIFE.
The core is divided into Solid inner core and Liquid outer core. The presence of large quantities of iron in the core is responsible for the Earth's gravitational force. As the Earth rotates on its axis, the liquid outer core spins over the solid inner core and generates the Earth's magnetic field. This is responsible for the functioning of the magnetic compass. Due to high pressure, the materials in the inner core are unable to move and hence remain solid.