Answer:
F Anthracite (the hardest coal)
Explanation:
Coal is a sedimentary rock that is formed from plant materials. These plant materials must have been trapped and compacted in an environment where they are not able decay. Such an environment is a swamp.
The first grade of coal that forms initially in such an environment is called PEAT. Peat is soft coal that still contains some plant materials. It has a high moisture content and the amount of carbon is still quite low.
With increasing pressure and compaction, PEAT grades into LIGNITE which has more carbon atoms in it. Lignite is more combustible although it is quite soft too. Lignite grades into SUB-BITUMINOUS coal and then BITUMIOUS coal.
The highest grade of coal is ANTHRACITE which is a hard coal. It has very little moisture content and rich carbon percentage in it. Anthracite yields more energy compared to other forms of coal. Anthracite is basically coal that forms at the greastest pressure. Beyond this pressure, a metamorphic transformation occurs and the coals changes to graphite.
Based on increasing pressure:
PEAT< LIGNITE< BITUMINOUS COAL < ANTHRACITE
Air rises at the equator, leading to low pressure and rainfall. Global atmospheric circulation creates winds across the planet and leads to areas of high rainfall, like the tropical rainforests, and areas of dry air, like deserts.
Mid- Atlantic ridge is a part of
constructive plate boundary or divergent plate boundary. This linear feature
lies in the midst of a two tectonic plates that are apart from each other.
Active divergent plate boundaries usually take place in the middle of oceanic
plates then become mid-oceanic ridges. In fact that a Mid- Atlantic Ridge is
mainly an underwater feature, some of its segments have an altitude that
extends above sea level. Its boundary is situated along Atlantic Ocean's bottom
and areas of the world's longest mountain range.
Answer:
The photosphere, the chromosphere and the ionosphere.
Explanation:
You did not list any layers in your question, however, the sun is composed of mainly 6 layers;
- The core
- The radiative zone
- The convective zone
- The photosphere
- The chromosphere
- The corona
The photosphere is the visible layer of the sun, however, it is very bright even when viewed with a telescope. A filter has to be used to reduce the intensity of the light. This filter is called a myler filter. It is added to the lens of the telescope. Using this, the photosphere can be seen using a telescope.
The chromosphere is an irregular layer above the photosphere. Due to the extremly high temperature, hydrogen emits light which gives off a reddish color. This is known as the H-alpha emmision. Therefore, to see this layer with a telescope, a special filter have to be fitted to the lens of the telescope. This filter is called the hydrogen alpha filter.
The corona is the outermost part of the sun atmosphere, however, it is hidden by the sun's bright surface. It can be seen during a total eclipse. This is when the moon covers the bright photosphere.
answer
It can change shape by erosion
