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Vast deposits of coal originate in former wetlands called coal forests that covered much of the Earth's tropical land areas during the late Carboniferous (Pennsylvanian) and Permian times. [3] [4] Coal is used primarily as a fuel. While coal has been known and used for thousands of years, its usage was limited until the Industrial Revolution.
Coal forms when organic matter builds up in waterlogged, anoxic swamps, known as peat mires, and is then buried, compressing the peat into coal. The majority of Earth's coal deposits were formed during the late Carboniferous and early Permian. The plants from which they formed contributed to changes in the Carboniferous Earth's atmosphere. [25]
Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System. Initially, Earth was molten due to extreme volcanism and frequent collisions with other bodies.
A general theory of basin-scale deposition has been formalized under the name of sequence stratigraphy. [3] Some cyclothems may have formed as a result of marine regressions and transgressions related to growth and decay of ice sheets, respectively, as the Carboniferous was a time of widespread glaciation in the southern hemisphere. [4]
Earth materials include minerals, rocks, soil and water. These are the naturally occurring materials found on Earth that constitute the raw materials upon which our global society exists. Earth materials are vital resources that provide the basic components for life, agriculture and industry .
Earth's outer core is a fluid layer about 2,260 km (1,400 mi) in height (i.e. distance from the highest point to the lowest point at the edge of the inner core) [36% of the Earth's radius, 15.6% of the volume] and composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. [31]
Before it split into the continents we know today, Earth was home to just a single landmass, or "supercontinent," called Pangea. Over tens of millions of years, as the familiar story goes, these ...
The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth itself.