Page 161 - General Knowledge

GENERAL KNOWLEDGE 2019

SUN

 The Sun is the star at the center of the Solar System.
 It is a nearly perfect sphere of hot plasma, with internal convective motion that generates
a magnetic field via a dynamo process.
 It is by far the most important source of energy for life on Earth.
 Its diameter is about 1.39 million kilometers (864,000 miles), or 109 times that of Earth,
and its mass is about 330,000 times that of Earth. It accounts for about 99.86% of the
total mass of the Solar System.
 Roughly three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly
helium (~25%), with much smaller quantities of heavier elements, including oxygen,
carbon, neon, and iron.
 The Sun is a G-type main-sequence star (G2V) based on its spectral class. As such, it is
informally and not completely accurately referred to as a yellow dwarf (its light is closer to
white than yellow).
 It formed approximately 4.6 billion years ago from the gravitational collapse of matter
within a region of a large molecular cloud. Most of this matter gathered in the center,
whereas the rest flattened into an orbiting disk that became the Solar System.
 The central mass became so hot and dense that it eventually initiated nuclear fusion in
its core. It is thought that almost all stars form by this process.

EARTHQUAKES

 Earthquakes are caused by the movement of the earth's tectonic plates.
 Earthquakes occur where the earth's plates meet along plate boundaries (see plate
tectonics page for more information on this).For example as two plates move towards
each other, one can be pushed down under the other one into the mantle.
 If this plate gets stuck it causes a lot of pressure on surrounding rocks. When this
pressure is released it produces shock waves. These are called seismic waves. This is
an earthquake.
 The waves spread out from the point where the earthquake started - the focus. More
damage is done near the focus.
 The point on the earth's surface directly above the focus is the epicentre.

Effects of Earthquakes

The effects of earthquakes vary. This is a result of a variety of factors such as the strength of
the earthquake, the level of population in an area and the level of economic development of the
area struck.

Measuring Earthquakes
The magnitude (size) of an earthquake is measured using a seismometer. This is a machine
that measures movements in the earth's surface.

The Richter Scale measures earthquakes on a logarithmic scale - this means that an

earthquake of 6 is ten times more powerful than one with a score of 5.

157 | P a g e shop.ssbcrack.com