Stalactites and stalagmites, How do they form?
828712
There is a great deal of erosion that occurs underground. Water that flows underground, called groundwater can erode rock, the result is a cavern. Caverns are often damp places. Many contain streams or lakes. Most have groundwater seeping into them from the ceiling. This water drips down to the floor of the cave. Often as the drip forms on the ceiling a small amount of sediment (usually calcium carbonate) is deposited on the ceiling When the drop hits the floor, a bit of sediment might be deposited as well. Eventually those deposits build up, sometimes building beautiful structures in the cave. When the deposits start on the ceiling and from and icicle-like structure hanging down the structure is a stalactite, when the deposits form a structure that rises from the ground, the structure is a stalagmite.
865007
Minerals are what make up rocks.  When Earth's rocks erode, these minerals are released.  A lot of times, erosion takes place in higher elevation areas because the denudation (erosion) rate of higher elevations is also higher than lower elevations and streams usually stem from places of higher elevation.  Minerals then are deposited into these streams.
268137
You'll have to consult a geology textbook to get a good answer on this.\n\nBasic answer: The shapes that the molecules take when they come together to form minerals, form in regular patterns.  That is, they align very regularly next to the last molecule.  The angles that these bond also form the angles at which the minerals form and cleve.
820047
Non-living things can increase in size, but only in response to external factors. Non-living things cannot "grow" from within as living things do. Stalagmites and stalactites "grow" by the deposition of minerals from without. Crystals "grow" by adding layers of the same mineral from without. A riverbed can enlarge as a result of erosion of its banks. A mountain range or volcanic peak can "grow" as a result of pressures pushing it up from beneath. A living thing grows by creating more of itself from within, by duplication of its own matter - its own cells.
1160643
maybe this can help\n\nhttp://en.wikipedia.org/wiki/Fossils
80631
I am not sure I understand your question so I will answer it two ways. Fossils are found in sedimentary rock because they originate as living organisms, and their remains will be carried away or buried by the same processes that create sedimentary rocks. Windblown sand will build and move sand dunes, moving water will transport sediment, gravity will cause piles of rock to build up at the base of mountains, and all sorts of sediment and remains will settle to the bottom of the sea. All are possible sedimentary rocks. Since igneous rocks were once melted, and metamorphic rocks undergo chemical changes from heat and pressure, it is not possible to find fossils in these rocks. \n\nMy second answer is how sedimentary rocks (and fossils) end up in layers. Many of the processes that move the sediment, like wind, flowing water, and some gravity driven events, only happen periodically. Storms create windstorms, heavy rainfall causes rivers to flood, and often things like heavy rain will trigger a sudden landslide. These events are distinct, and each one will create a new layer of deposits somewhere. Another way these layers are created is that rivers will often change course due to changes in flow. This will cause areas that have accumulated sand to now be covered by silt or shale when the river overflows its new channel. As the river builds a delta outward into the ocean, the part of the delta where the river first meets the ocean will deposit sand, while clays and silt are carried further out into the ocean. This will create layers of shale that are later covered by sand. Within each of these layers fossils of any organism that died while those were being deposited will be trapped, and the fossils in turn can be used to calculate the age of those deposits. Every layer of a sedimentary rock represents some event in the history of the earth. \n\nIn limestone, which has a very high content of fossils, the reason for this is that the limestone is built by the accumulation of the body parts left behind by those organisms. The fossils in limestone may not be transported at all, and instead may be in same place the organism lived (in relation to the immediate rock). Layers in limestone are more often created by rising and falling of sea level. As sea level raises many organisms that end up as limestone will die off. They will then be covered by a layer of sediment falling from the overlying water, and if sea level drops again, new organisms will begin to colonize the shallower water and build another layer of limestone.
654586
Igneous rocks-- formed from magma, extrusive or intrusive.  extrusive have small crystal forms ex. basalt, scoria, pumice.  Intrusive large crystals forms ex. granite, gabbro\n\nSedimentary rocks -- the only rocks that contain fossils, formed at the surface, formed from fragments of other things ie. rocks, fossils, woody plants (coal), or minerals crystallizing out of water (limestone) -- Are porous found in aquifers, oil fields.\n\nMetamorphic rocks -- forms from alteration of other rock with increased pressure and/or temperature.  Always in a solid state (they don't melt)called recrystallization, form new minerals that are stable at increased temperature and/or pressure, happens below the earth's surface (at depth).
503652
False. Caves are found in permeable rock called limestone. Naturally occurring acids dissolve the rock to produce the caves.\n\nThe clue here is containing water. Permeable rock can contain water whereas impermeable rock is resistant to water moving through it.
34741
Sedimentary rocks can be divided into two major informal groups, referred to as clastics (or siliciclastics) and carbonates. Clastic rocks are formed by erosion of other rocks, igneous, metamorphic and sedimentary. These 'clasts' can be mud, silt, sand, cobbles, or boulders, and are transported by wind, water, or gravity and accumulate where they eventually are buried and pressure and temperature subject them to diagenesis, the process that makes them from unconsolidated clasts to one rock mass. Shale, sandstone, and conglomerate are examples of clastics.\n\nCarbonates can work much differently since they form primarily in the oceans. Many carbonates are made from reefs and other living organisms that grow in the ocean. As these organisms die and leave behind their carbonate skeletons, rocks are formed. Other carbonates are formed from small grains called ooids, small balls that form by precipitating out of sea water, possibly with the help of bacteria or algae. Some ocean algae even form carbonate 'mud' that eventually becomes hard rock. \n\nAnother unusual group of sedimentary rocks are called evaporites. These are rocks like gypsum and rock salt that are deposited by evaporation of water in confined basins. \n\nThe most fascinating part about sedimentary rocks is that they have a past, each one tells a story.
1076848
the simplest explanation is as follows:\n\n* igneous rocks are formed when molten lava is erupted on to the earth's surface and cools. i.e. basalt lavas. \n\n* sedimentary rocks are formed when other rocks (possibly igneous, metamorphic or previous sediemtnary rocks) are eroded chemically or physically and are then redeposited. i.e. sandstones and mud stones.\n\n* metamorphic rocks are formed when other rocks (igneous or sedimentary typically) are buried and then exposed to high temperatures and pressures that change the properties of that rock. i.e. marble - metamorphosed limestone.
211516
# Snow: Falling ice composed of crystals in complex hexagonal forms. Snow forms mainly when water vapor turns directly to ice without going through the liquid stage, a process called sublimation.\n# Snowflakes: Aggregations of snow crystals.\n# Snow flurries: Light showers of snow that do not cover large areas and do not fall steadily for long periods of time.\nHail: Falling ice in roughly round shapes at least 0.20 inch in diameter. Hail comes from thunderstorms and is larger than sleet. Hailstones form when upward moving air -- updrafts -- in a thunderstorm keep pieces of graupel from falling. Drops of supercooled water hit and freeze to the graupel, causing it to grow. When the balls of ice become too heavy for the updrafts to continue supporting them, they fall as hailstones. Sleet, in contrast, consists of raindrops that freeze on the way down.
922588
Wow, this would take a book to explain in detail!  I'll try to explain as briefly as I can. \n\nMost minerals are crystals*.  \n\nCrystals are basically formed by an arrangement of atoms in a pattern that repeats itself in 3D.  They start as a small cluster of atoms which grows into a recognisable crystal as more atoms are attracted by the electrical forces of those already in the crystal structure.  \n\nCrystals are formed mainly from molten solids (such as in molten magma) and solution (in water) and less often, from vapors (i.e. gases).  \n\n* Some minerals are not crystalline.  E.g. Opal, Obsidian.  These exhibit an amorphous character, meaning they have no crystal form or structure.  \n\nHope that helps a little!
951858
Evaporites (IPA: /iˈvapərʌɪt/) are water-soluble, mineral sediments that result from the evaporation of bodies of surficial water.\n\nEvaporites are formed by evaporation of restricted bodies of water at the Earth's surface.\n\nAlthough all water bodies on the surface and in aquifers contain dissolved salts, in order to form minerals from these salts, the water must evaporate into the atmosphere in order to precipitate the minerals.\n\nIn order for this to happen the water body must enter a restricted environment where water input into this environment remains below the net rate of evaporation. This is usually an arid environment with a small basin fed by a limited input of water.\n\n--> http://en.wikipedia.org/wiki/Evaporite#Evaporitic_formations\n\nSedimentary rocks are laid down in layers called beds or strata. Each new layer is laid down horizontally over older ones. There are usually some gaps in the sequence called unconformities. These represent periods in which no new sediments were being laid down, or when earlier sedimentary layers were raised above sea level and eroded away.\n\n--> http://en.wikipedia.org/wiki/Sedimentary_rocks
331538
3 basic types of rocks\n\nIgneous Rocks-Igneous rocks are crystalline solids which form directly from the cooling of magma. This is an exothermic process (it loses heat) and involves a phase change from the liquid to the solid state. The earth is made of igneous rock - at least at the surface where our planet is exposed to the coldness of space. Igneous rocks are given names based upon two things: composition (what they are made of) and texture (how big the crystals are).\n\nSedimentary Rocks-In most places on the surface, the igneous rocks which make up the majority of the crust are covered by a thin veneer of loose sediment, and the rock which is made as layers of this debris get compacted and cemented together. Sedimentary rocks are called secondary, because they are often the result of the accumulation of small pieces broken off of pre-existing rocks. There are three main types of sedimentary rocks:\n\nMetamorphic Rocks-The metamorphics get their name from "meta" (change) and "morph" (form). Any rock can become a metamorphic rock. All that is required is for the rock to be moved into an environment in which the minerals which make up the rock become unstable and out of equilibrium with the new environmental conditions. In most cases, this involves burial which leads to a rise in temperature and pressure. The metamorphic changes in the minerals always move in a direction designed to restore equilibrium. Common metamorphic rocks include slate, schist, gneiss, and marble.
129822
You've been given exhaustive lists, copied directly from websites without giving proper citation I imagine. \n\nHere is how to think about this question so that you can recall and understand the answer, without just memorizing a bunch of rock names.\n\nUse the rock cycle. Igneous rocks are of two groups, those formed within the earth and those formed by volcanism.  The volcanic rocks will show signs of that volcanism and will be things like black columnar basalt found in massive flows. Obsidian (volcanic glass) that flowed as liquid, scoria and pumice which are like foam because the dissolved gases expanded and made them bubble as they hardened. The other igneous group formed under the earth's surface, and includes things like granite where you can see the crystals that formed as it cooled and solidified. \n\nSedimentary rocks are also in two major informal groups (and a minor third). The first group of sedimentary rocks is clastics. These are formed by weathering, transport and deposition. Weatherings breaks down rocks like igneous, metamorphic and even sedimentary rocks and transport by wind, water, or gravity deposits these rocks as accumulations of clasts, (thus clastics). They become sandstone, shale, and conglomerate. The other major sedimentary group is carbonates. These rocks are 'born' because they are formed by living things. Ocean environments (and lakes too) have many organisms that make shells, corals that make reefs, and algae that make fine carbonate sediments (known as carbonate mud). Even bacteria get into the act helping to precipitate carbonates in many ocean environments. The third group of sedimentary rocks is those that are dissolved by water and deposited by evaporation or precipitation. These include gypsum, halite, sylvite, and many more. \n\nMetamorphic rocks all start life as one of the previous groups. You can metamorphose a granite into a granitic gneiss by burial, pressure and heat. You can metamorphose a basalt into an amphibolite. You can make limestone into marble. Sandstone turns into quartzite.\n\nRemember the rock cycle, associate the rocks as they move through it, and you won't have trouble remembering examples of rock types. Also don’t get tripped up by the difference between a mineral and a rock. Geologists sometimes use the two terms identically, but there is a formal difference between a rock (which is an impure mixture) and a mineral that is chemically consistent.
586740
There are three basic types of rocks: igneous, sedimentary, and metamorphic.\n\nIgneous rocks are formed from molten magma or lava. Igneous rocks vary greatly in grain structure and size, depending upon how quickly the magma or lava cooled. An example of an igneous rock is obsidian.\n\nSedimentary rocks are formed when layers of sediment are compacted by pressure. They are often composed of fragments of materials derived from other rocks and minerals, especially quartz.\n\nMetamorphic rocks occur when igneous, sedimentary, or previously-formed metamorphic rocks are submitted to extreme heat or pressure beneath the earth's surface, changing their structure and appearance. They often exhibit "foliation" or color banding when mineral crystals are elongated due to pressure. An example of a metamorphic rock is slate.
869704
Igneous, metamorphic, and sedimentary rocks all have the potential to become one of each of the other types of rock through the rock cycle. Igneous and metamorphic rocks can be broken down into rock fragments and cemented to form a sedimentary rock. Sedimentary or igneous rocks can undergo changes in temperature and pressure to form metamorphic rocks. And all three types can be melted and reformed as igneous rocks.