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Rocks at Earth

IN SHORT - Most Earth's rocks originate either at the time of our planet's formation, or from more recent events, like tectonics, erosion, or volcanism, with, over the eons, ancient sea-floors transformed into high mountains and rivers taking back to the ocean the rocks they take from the mountains and hills. Igneous, sedimentary, and metamorphic rocks

s are the main categorization of Earth's rocks with the rocks originating in the magma, the erosion process of igneous rocks, or the re-processing at great pressure of both the first categories, respectively. Most rocks found at Earth formed from 8 basic elements, oxygen, silicon, aluminum, iron, magnesium, calcium, potassium, and sodium

Earth is a rocky world. As a planet of the inner solar system it formed mostly of dense material existing into primordial planet building blocks called planetesimals. Sun radiation had blown more volatile elements, like ice and gas, away from this part of the solar system. Once aggregated into a Moon-size body these primordial materials heated and differentiated, forming a core, a mantle, and a crust. Most rocks Earth originated from this process as from further long-term processes like tectonics, erosion or volcanism. Earth's surface was shaped and transformed over eons, manufacturing rocks and manufacturing some again. Nowadays ancient ocean bottoms may be seen at highest mountains' summits as volcanic ridges are creating new rocks in the middle of the oceans or water streams are taking to the sea material taken along their course

The Earth formed 4.5 billion years ago, as August 2007 studies have shown that the crust might have taken 200 million years only to form, based on the discory of rough diamonds found in Australia, instead of the 400 millions usually thought. Such a hint to the existence of rocks at such an early time, on the other hand, might too be the sign that the Earth then also had an ocean, and life maybe

Igneous Rocks

Any rock Earth originated in the hot magmatic material which formed when the building blocks endured heating and eventually formed the core, the mantle and the crust of our planet. These very first rocks are termed "igneous", or volcanic, rocks. According to how their solidification process unfolded igneous rocks are further classified. Slowly cooling magma (this usually occurred at depths of thousands of feet) gave coarse-crystals rocks like granite. Such rocks are of the "macrolithic" type. When magma cooled more swiftly (this usually occurred near or at the surface), this gave smaller crystals and fine-grained rocks like basalt ("microlithic" rocks). When the solidification occurred abruptly this gave other types of rocks like the tuff and other light volcanic products (amorph rocks). These different types of igneous rocks may have been combined and formed further varieties like coarse-crystals rocks embedded into fine-grained rocks (porphyry) or fine-grained rocks into amorph rocks (like trachytes)

Sedimentary Rocks

These rocks mostly formed due to erosion processes working at the igneous rocks. Water and wind e.g. eventually weared the igneous rocks as materials were carried away, accumulating in lakes, oceans or on land. Material settled into layers of sediments and formed back rocks -the sedimentary rocks. Rock formation based upon bonds by minerals and chemicals or electric attraction. Such process might further work with animals or plants debris. It may too stop short of forming a really agregated rock, forming loose and unconsolidated rocks only. Sedimentary rocks are always found in layers parallel to Earth surface. When the layers are twisted, broken or at a high angle with the surface, this is the evidence that some geological process occurred. Sedimentary rocks are further classified into three categories: clay and shale-type rocks (based on mud), chalks (marine creatures), sand-based rocks (sandstone)

Metamorphic Rocks

Enduring intense pressures and temperatures deep under the surface or due to volcanic processes, both igneous and sedimentary rocks may be transformed into "metamorphic" rocks (it's what the term means in Greek: "meta-morphein", "beyond-form"). Metamorphism is acting on the original rocks by making them denser and more compact only. Clays and shales are giving schists, granite is giving gneiss and micaschists, chalk yields marble, as sandstone quartzites. Oldest metamorphic rocks are often ore or gem-rich

Generally, most rocks formed from 8 elements only (oxygen, silicon, aluminum, iron, magnesium, calcium, potassium, and sodium). These elements may be combined in various ways and they were along Earth geological history. Hence thousands of types of rocks and minerals exist on Earth. No rock earlier than 3.9 billion years ago have been found although Earth being 4.5 billion years old. This is due to all older rocks having been transformed into new rocks during Earth earliest geological times