Question 1
Convection is organized by the circular motion of water flow or air through thermal changes in the density and gravitational attraction, which originate from the source of heat and decrease in the colder outer layers.
Craton is a lithosphere platform with the foundation of Precambrian age.
Earthquake magnitude is a scale characterizing the energy released during an earthquake in the form of seismic waves.
Focus is an area of occurrence of underground hits in the earth's crust or upper mantle, resulting in an earthquake.
Epicenter – is the central point of the surface of the earthquake focus.
Isostasy is hydrostatic equilibrium state of the earth's crust, when the Earth's less dense crust "floats" in a dense layer of the upper mantle – asthenosphere, subject to the law of Archimedes.
Isotope – species of a chemical element that have the same number of protons, but different number of neutrons in their nuclei.
Magma – is a lava that erupted on the surface of the Earth.
Felsic – igneous rocks which are specific by the content of silica (SiO2), which varies between 63-78%.
Mafic – igneous rocks relatively poor in silica (55%) and rich in calcium and magnesium.
Lithosphere – solid shell of the Earth. It consists of the crust and upper mantle, up to the asthenosphere.
Asthenosphere is a layer in the upper mantle of the Earth. It is more plastic than its neighboring layers.
Transform boundary is a type of lithosphere fracture, which is located along the plate boundaries.
Question 2
The Earth lacks impact craters because of the atmosphere which safeguards the planet from meteorites impact. Only those weighing more than 1,000 tons reach the Earth's surface. But impact craters after them soon vanish being rapidly destroyed by erosion.
Question 3
A mineral is natural homogeneous solid substance, which is now or formerly was in the crystalline state. Minerals are an integral part of rock (rock-forming minerals), ores, and meteorites.
Question 4
Question 5
Continents have such shapes as if they were separated as jig-saw puzzle pieces.
Mountains were formed as a result of plates pushing against each other.
Plate boundaries are known for their active volcanic and seismic activities.
Comparison of fossils at the edges of whole continents suggests that these fossils were previously jointed.
Question 6
Question 7
The theory of plate tectonics originates from the theory of continental drift. According to it, there were two continents – Laurasia and Gondwana, a sea Tethys., and an ocean Panthalassa. About 200 million years ago, Gondwana and Laurasia were combined into a single continent – Pangea. But approximately 180 million years ago, the continent Pangea again began to get separated into its component parts, which mixed on the surface of our planet.
Question 8
There are such types of earthquake waves: body waves and surface waves.
Body waves pass through the Earth's interior. They include primary waves and secondary waves. Primary waves are longitudinal or compression waves, they may pass through any material. Secondary waves are transverse waves and can operate only in solids.
Surface waves are somewhat similar to the waves of water, but unlike them, they travel through the earth's surface. Their usual speed is significantly slower than body waves. There are of two types of such waves: Rayleigh waves and Love waves.
Question 9
Earth's magnetic field exists because the internal structure of the globe is magnetic. External factors that determine the existence of Earth's magnetic field are natural systems of electric currents in the ionosphere. The magnetic field protects everything alive from cosmic rays. Planets without a magnetic field are doomed: no forms of life can survive due to an excess of cosmic rays.
