Earth and Its Structure

Horse Latitudes or Subtropical High are subtropical latitudes between 30 and 35 degrees both north and south. This region, under a ridge of high pressure called the subtropical high, is an area which receives little precipitation and has variable winds mixed with calm. The horse latitudes are associated with the subtropical anticyclone and the large-scale descent of air from high-altitude currents moving toward the poles.

Following are the evidences of the Earth’s shape:

1. Earth's shadow on the moon (at lunar eclipse) is always circular.
2. The position of the sun and the stars depends on the position of earth, thus earth has to be curved.
3. Magellan sailed around Earth.
4. Yuri Gagarin orbited Earth in space.
5. Pictures of Earth taken from the Moon impressively demonstrate the shape of Earth.
6. The rotation of Earth can be proven with Foucault's pendulum.
7. Astronomical observations show that all the other planets are spheres, it is very likely that the Earth is a sphere too.

S-wave, secondary wave or shear wave (sometimes called an elastic S-wave) is one of the two main types of elastic body waves. S-wave moves as a shear or transverse wave, so motion is perpendicular to the direction of wave propagation. S-waves are like waves in a rope.
Unlike P-wave, S-wave cannot travel through the molten outer core of the earth and this causes a shadow zone for S-waves opposite to where they originate.

Density of the layers of the earth:
Continental crust: 2.7 to 3.0 g/cm³
Oceanic crust: 3.0 to 3.3 g/cm³
Mantle (silicates): 3.3 to 5.7 g/cm³
Outer core (liquid): 9.9 to 12.2 g/cm³
Inner core (solid): 12.6 to 13.0 g/cm³
Average density of the earth: 5.5 g/cm³

P waves are also known as compressional waves, because of the pushing and pulling they do.
Subjected to a P wave, particles move in the same direction that the wave is moving in, which is the direction that the energy is traveling in, and is sometimes called the 'direction of wave propagation'.
S-wave moves as a shear or transverse wave. So, motion is perpendicular to the direction of wave propagation.
L-waves and Rayleigh waves both are types of surface waves.

Density of the layers of the earth:
Continental Crust: 2.7 to 3.0 gm/ cm³
Oceanic Crust: 3.0 to 3.3 gm/ cm³
Average density of the earth: 5.5 gm/ cm³
The earth can be divided into crust, mantle and core on the basis of its chemical composition.

Knowledge of the earth's interior is based on the reactions of seismic waves from earthquakes; the density and state of materials that these seismic waves encounter.
Some of this understanding is based on our current understanding of how the earth formed - mainly, how our planet cooled down and formed; how the heavier materials such as metals sunk to the center, etc.
Rock that is torn off and expelled by volcanism is studied as another indicator of what lies below the surface.
Another clue lies in meteorites that have landed on earth.
The study of earth's magnetic field and gravitational properties also indicate or strongly infer what lies deep in earth's interior. 

P - waves are the first waves to reach the earth's surface from the interior of the earth.
L - waves are one of the types of surface waves.
S - waves are transverse in nature, similar to light waves.
P - waves can transmit both through solids and liquids.

Option 1 correctly matches the Discontinuities with their zone in the earth's interior

P-waves are the first to arrive, i.e. they travel fastest. These are 'push-pull' waves analogous to sound waves, in which each particle moves back and forth.
S wave is the secondary wave. It is a transverse wave, which means the particles of its medium move at right angles to the energy that is being transferred. S waves are analogous to ocean waves, as the water molecules oscillate only up or down while the wave itself can move many miles from the origin.

Mohorovicic discontinuity separates mantle from crust.
Earth's mantle is a rocky shell about 2,900 km thick that constitutes about 84% of Earth's volume.
Note: Earth's radius is 6,400 km
Lehman discontinuity separates inner core from core.

The correct match list i

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling.
In general, the composition of lava determines its behaviour more than the temperature of its eruption.
Acid lava comes from composite cone volcanoes, is slow moving and viscous. Basic lava comes from shield volcanoes, is runny and flows faster. Acidic lava is felsic, or high in quartz and potassium feldspars. Basic lava is mafic and higher in plagioclase feldspar.

Epeirogenic forces are vertical forces, wherein the continents either rise or sink under the influence of these forces. Also called continent-building forces. E.g. Subsidence. Orogenic forces are horizontal forces that either push or pull rock strata. Also known as mountain-building forces. E.g. folding.
Eustatic sea level changes are due to the glacial-interglacial cycle, with water being tied up in continental ice caps during glacial periods, thereby lowering the sea level, and when the ice caps melt, the water flows into the sea and raises the sea level.
Exogenetic forces/agents of erosion are, generally, destructive.