Geology.com offers many pictures of rocks, divided into their fundamental categories of igneous, metamorphic and sedimentary. The igneous rock section divides the rocks into extrusive and intrusive types, with special sections for gabbro, peridotite, tuff and others. The metamorphic rocks are divided into foliated and non-foliated rocks, with 10 separate sections focusing on marble, schist, gneiss and other rocks.Continue Reading
Geology.com further divides sedimentary rocks into clastic, chemical and organic types, with a dozen sections devoted to conglomerate rocks, limestone, siltstone and more.
In addition, the site offers pictures of rocks and explanations of special phenomena regarding rocks such as the sliding rocks of racetrack playa. Further pictures are available of rocks on Mars, which appear to be very similiar to rocks on Earth. Another section offers pictures of lava, explaining and showing how a rock can be molten and liquid.
One gallery of pictures features types of sand from all over the world, with photos of exotic orange, green, black and white sands, among others. A separate photo gallery shows the beauty of individual grains of sand. Another close-up set of photos focuses on the beauty of coal when seen through a microscope.
One further startling photo gallery shows a rockfall at Yosemite National Park, along with the accompanying debris avalanche.Learn more about Geology
Sedimentary rocks are primarily characterized by lithification. Lithification occurs when sediment has been deposited and accumulates at the earth's surface or in bodies of water to form a rock over time. Subgroups of sedimentary rocks are defined by their specific formation.Full Answer >
Frac sand is high-purity quartz sand with durable and round grains that the petroleum industry uses for hydraulic fracturing, also called fracking, to produce petroleum fluids, including gas, natural gas and natural gas liquids, from rocks that do not have enough pore space for the liquids to flow to a well. Hydraulic fracturing requires thousands of tons of sand for each well, which created a billion dollar frac sand industry.Full Answer >
Magma forms when rocks in the mantle melt due to changes in pressure or the addition of water. Although temperatures in the earth's mantle are much hotter than melting temperature, there is not a layer of magma or molten rock under the earth's surface at any given time because there is too much pressure for rock to melt. Rather, magma forms here and there because of certain changes.Full Answer >
Sedimentary rocks are characterised by their formation from the deposition and lithification of rock material. They may be formed through physical and chemical processes, such as mechanical weathering, compaction and dissolving of rock material.Full Answer >