Igneous rocks: Peridotite
By: J. Lang Wood
Peridotite is an igneous type of rock that is composed primarily of olivine. Peridotite has a coarse grain and may contain small amounts of other elements, such as spinel, chromite and plagioclase and amphibole. Peridotite is abundant on Earth and has a number of uses...
How earthquakes are caused
By: Sarah Cagle
Figuring out the cause of earthquakes has puzzled scientists for centuries. In fact, today they still only have theories about the exact cause of earthquakes. While they know a lot about the general cause of earthquakes, they know very little about their precise origins. In...
By: Mari Mckee
Schist is a medium grade metamorphic rock following shales, slates, and phylittes, in the rock cycle of metamorphism. Schist means “to split” which is a hallmark of this rock. Schist can be formed from the igneous rock basalt (orthoschists); or from shale, a sedimentary...
Metamorphic rocks: Phyllite
By: Jose Juan Gutierrez
Phyllite is a fine-grained metamorphic rock formed from sedimentary rocks, such as shale and mudstone. A metamorphic rock is created when existing rock is physically and chemically transformed by intense heat and pressure. Phyllite is metamorphosed from shale, its protolith or parent rock. At intermediate...
By: Patricia Jankowski
Peridotite is an igneous rock, which means that it was formed after molten lava cooled and solidified. It is composed mostly of olivine (a mineral which, when it is gem quality, is the beautiful peridot found in jewelry) and pyroxene, a silicate mineral. It is...
Metamorphic rocks: Quartzite
By: Jose Juan Gutierrez
Quartzite is a non-foliated metamorphic rock composed in its majority of quartz, and formed from the sedimentary rock sandstone. A metamorphic rock is formed when constituent minerals recrystallize in a new molecular arrangement due to tectonic compression and heating. Quartzite is transformed from, its protolith...
Metamorphic rocks: Schist
By: Jose Juan Gutierrez
Schist is a foliated regional metamorphic rock formed from basalts or slate. Schist forms at higher metamorphic grades than slate, although the protolith of both rocks may be the same parent rock stone. Regional metamorphism is caused by Earth’s internal geologic processes, including the...
By: Hai Shunxi
When people think of rocks, they think of something hard and heavy: we even say that something that doesn't float "sinks like a rock." That's usually true, but there is one fascinating rock type that simply doesn't follow the rules: that rock is pumice...
Volcanoes, what they do and how they're formed
By: Jose Juan Gutierrez
A volcano is a geological fracture or opening in the Earth's crust caused by tremendous internal forces, such as pressure and temperature inside the Earth. These dynamic internal forces push magma and gases up through a volcano's vent. Once these volcanic materials reach the surface...
What are stratovolcanoes?
By: Jose Juan Gutierrez
Stratovolcanoes (composite volcanoes) are steep-sided, conical volcanoes. They are formed by many layers of hardened lava flows, pyroclastic flows and lahar flows. Stratovocanoes are most often formed on continental land, and have gentle slopes at the base that gradually rise until they reach their steepest...

 

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