Rocks and Minerals
Erosion and Weathering
Oceans and Seas
Do you ever wonder why one river is straight and flows quickly while another meanders along curves and seems to be slow and peaceful, or how the mountains were formed? Geology is the study of the earth, its materials, and the processes acting upon them. It includes the study of rocks and minerals; and their formation, weathering, and metamorphosis. So, when you need an answer to a question about rivers, mountains, volcanoes, rock cycles, plate tectonics, or other geological aspects, our Geology category is the place to ask it.
What is the difference between a rock and a mineral?
A rock is formed from minerals; a mineral may be considered as a chemical compoud with a chemical formula. The rock is a mixture. ...
Asked in Geology, Erosion and Weathering
What are the differences between weathering and erosion?
Weathering is the breaking down of rock into smaller and smaller particles. Weathering processes include frost wedging, acid rain dissolution, root growth, wind particle abrasion, heat expansion cracking, hydraulic fracture, and rock tumbling in rivers and streams. Erosion is the movement of weathered material from one place to another place through the agents of erosion: wind, water, ice, and gravity. In tandem, weathering and erosion act to lower the high points, and raise the low points on the surface of the planet. ...
Asked in Geology, Mountains, Valleys
How are mountains formed?
Volcanic mountains are formed either through the introduction and accumulation of magma over a crustal "hot spot" or through volcanic activity associated with the collision and subduction of a crustal plate, where the melting of the subducted crust creates magma, gases and pressures that are released in eruptions. Continental crustal plate collisions, where neither plate subducts, create mountain ranges such as The Himalayan Mountain Range, where crustal material is thrust upward faster than erosion can wear it down. Plates can stretch until they crack and...
Asked in Geology, Paleontology, Fossils
How do you determine the age of a sedimentary rock or a fossil contained within it?
This an area of common misconception. Most sedimentary rock, and the fossils contained therein cannot be dated directly with radiometric techniques, but can be dated indirectly. Here's the facts: Because most sedimentary rock is composed of particles of pre-existing rock of various types, each particle can be a different age. Carbon-14 or carbon dating techniques can only be used to date organic material which is of a maximum age of 70,000 years; this leaves out the vast majority of fossils found in rock, and...
Asked in Science, Geology, Planetary Science
How do crater counts tell us the age of a surface?
The more craters a surface in space has (e.g. moon's surface), the older it is likely to be. A surface which has been around longer will have been exposed to more impacts from objects such as meteorites. In addition, if you are able to get figures for the rate of crater production, it is possible to use the number of craters to give an quantitative estimate of the age of the surface. ...
Asked in Geology, Rocks and Minerals
6 methods to tell minerals apart?
Six methods to tell minerals apart? 1) Acid test = will it bubble? is there a light, strong, or no reaction to the acid 2) color= white, black, green, pink, or gold 3) streak= black. Brown. White. Red. This tests the powder color of the mineral 4) luster= dull, pearly, shiny 5) weight = gravity test 6) hardness= this is a scratch test mineral against a penny and a file. ...
Where do you find geodes in California?
The Hauser Geode Beds, SW of Blythe, offer good geode collecting in several different areas. For further details, it's best to join a local gem and mineral club, consult your state geology department, or a local university or museum's earth science department. ...
Asked in Geology, Jewelry, Chemistry, Elements and Compounds
What elements do alexandrite contain?
Alexandrite is the highly regarded color changing variety of Chrysoberyl. The color of Alexandrite changes under different lighting conditions. If viewed in daylight, its color is greenish blue to dark yellow-green. If viewed in incandescent or candle light, its color is pink to red. Its chemical formula is BeAl2O4, it has a hardness of 8.5 on the Mohs scale and a refractive index of 1.744 - 1.755. Source: http://www.minerals.net/gemstone/alexandrite_gemstone.aspx ...
Asked in Geology
What is mineralogy and what does a minerologist do?
mineralogy is the study of minerals and a minerologist specifically studies minerals there chemistry, molecular bonds, miller indices, and assorted specific features of minerals. ...
Asked in Geology, Rocks and Minerals
Is limestone the hardest rock?
No, far from it. Limestone is actually quite soft, rating only a 3 or 4 on the Mohs scale. Care should be taken when making generalisations about rock properties. Hardness is a function of a material's elastic modulus (how much it deforms under a given load). Limestone (like all rocks) is a natural Earth material. As such it can display a very large variability in properties. For example limestones can have Young's modulus values ranging from 9 to 70 MPa.[A] This is clearly very...
Where are the oldest rocks in the atlantic ocean found?
The Atlantic Ocean started to form about 200 million years ago, shortly after the beginning of extensive volcanic activity, associated with tensions in the continental crust between nowaday's Afrika and North America. The oldest oceanic crust in the Atlantic Ocean is therefore found off the continental slopes of the USA and Northwest Africa. The continental shelfs, of course, comprise rocks below their sedimentary cover that often are much older than the oldest oceanic crust. ...
Asked in Geology, Chemistry, Mining
What are the uses of limestone?
Limestone Uses: Used as aggregate or base for roads and foundations. Used in the purification of molten glass. Used to remove impurities from molten iron. Used as filler and abrasive in toothpastes. Used in the production of Portland cement. Used as an aggregate in concrete. Used as a soil conditioner for neutralizing acidic soils. Used as a source of calcium in supplements and food additives. Used to make paper white. Used in the purification of sugar. Used in the manufacture of brake pads. Used in the manufacture of...
Asked in Technology, Geology, Earth Sciences
What are windows to earths interior?
Mantle-derived xenoliths. The magma is mantle and/or subducted-crust-derived. Xenoliths come from the country rock through which the magma rises, so really it's the magma (solidifying as igneous rock) that's the window. For greater depths, seismic analysis is the window. ...