Hey there! I’m researching rocks because I’m curious about them. I also like rocks because they are so interesting. Enjoy!
Geologists define rocks as aggregate of minerals. Minerals are naturally occurring, not unhealthy substances with specific chemical compositions and structures. A rock can be filled of many crystals of one or more minerals, or combinations of many minerals. Several exceptions, such as coal and obsidian, are not composed of minerals but are thought to be rocks.
People often use rocks for include building materials, roofs, sculpture, jewelry, tombstones, chalk, coal for heat, and more. Oil and natural gas can also be found in rocks. Many metals like a fork are made from rocks known as ores. Even, prehistoric humans used rocks as early as 2,000,000 B.C. Flint and other hard rocks were very important raw materials for crafting arrowheads and other special natural made rocks.
Around 500,000 B.C., rock caves and structures made from stones had become important forms of shelter for early man. During that time, early men had learned to use fire, a development that allowed humans to cook food as needed to survive and greatly expand their geographical range. Eventually, most likely no sooner than 5000 B.C., humans had realized that minerals such as gold and copper could be from rocks. Tons of ancient monuments were crafted from stone, including the pyramids of Egypt, built from limestone about 2500 B.C., and the buildings of Chichen Itza in Mexico, also of limestone, built near A.D. 450.
Since the 1500s, scientists have studied minerals and mining, fundamental aspects of the study of rocks. Georg Bauer published Concerning Metallic Things in 1556. By 1785, the British geologist James Hutton published Theory of the Earth, in which he explained his observations of rocks in Great Britain and his conclusion that Earth is much older than previous scientists before him had guessed. Geologists are scientists who study the earth and rocks, distinguish three main groups of rocks: igneous rocks, sedimentary rocks, and metamorphic rocks.
These distinctions are made on the basis of the types of minerals in the rock, the shapes of individual mineral grains, and the overall texture of the rock, all of which indicate the environment, pressure, and temperature in which the rock was made. Igneous rocks form when magma is below the land of the Earth or lava at the land of the Earth hardens. The minerals in the rock will make crystals or grow together so that the separate crystals make 1 crystal altogether. Igneous rocks and magma make up much of the oceanic and continental crust, as well as most of the rock deeper in the Earth.
Igneous rocks can be identified by the interlocking appearance of the crystals in them. Typical igneous rocks do not have a layered texture, but exceptions exist. For example, in large bodies of igneous rock, relatively thick crystals that are made early can sink to the bottom of the magma, and less thick layers of crystals that are made later can accumulate on top. Igneous rocks can form deep within the Earth or at the surface of the Earth in volcanoes.
In general, igneous rocks that form deep within the Earth have large crystals that indicate a longer period of time during which the magma cools. Igneous rocks that form at or near the surface of the Earth, such as volcanic igneous rocks, cool quickly and contain smaller crystals that are difficult to see without magnification. Obsidian, also called volcanic glass, cools down so fast that no crystals are made. Nevertheless, obsidian is considered to be an igneous rock.
Igneous rocks are classified on the basis of how much minerals there are and the size of the crystals in the rock. Extrusive igneous rocks have small crystals and crystallize at or near the Earth’s surface. Intrusive igneous rocks cool slowly below the Earth’s surface and have larger crystals. Rocks made up of thick, dark-colored minerals like olivine, pyroxene, amphibole, and plagioclase are called mafic igneous rocks.
Light-colored, less thick minerals, including quartz, mica, and feldspar are called felsic igneous rocks. Common igneous rocks include the felsic igneous rocks granite and rhyolite, and the mafic igneous rocks gabbro and basalt. Granite is an intrusive igneous rock that includes large crystals of the minerals quartz, feldspar, mica, and amphibole that form deep within the Earth. Rhyolite includes the same minerals, but forms as extrusive igneous rock near the surface of the Earth or in volcanoes and cools quickly from magma or lava, so its crystals are difficult to observe with the naked eye.
Similarly, gabbro is more coarse-grained than basalt and made deeper down in the Earth, but both rocks include the minerals pyroxene, feldspar, and olivine. Fabulous exposures of igneous rocks occur in the volcanoes of Hawaii, volcanic rocks of Yellowstone National Park are located in Wyoming, Idaho, Montana, in Lassen Volcanic National Park and Yosemite National Park in California. Sedimentary rocks are those made of grains of preexisting rocks or organic material that, in most cases, have been eroded, deposited, compacted, and cemented together. They typically form at the surface of the Earth as sediment moves as a result of the action of wind, water, ice, gravity, or a combination of these.
Sedimentary rocks also form as chemicals precipitate from seawater, or through accumulation of organic material such as plant debris or animal shells. Common sedimentary rocks include shale, sandstone, limestone, and conglomerate. Sedimentary rocks typically have a layered appearance because most sediments are deposited in horizontal layers and are buried beneath later deposits of sediments over long periods of time. Sediments deposited rapidly, however, tend to be poorly layered if layers are visible at all.
Sedimentary rocks are made in many different environments at the surface of the Earth. Eolian, or wind blown, sediments can accumulate in deserts. Rivers carry sediments and deposit them along their banks or into lakes or oceans. Glaciers make unusual deposits of a wide variety of sediments that they pick up as the glacier expands and moves; glacial deposits are well exposed in the northern United States. Sediments can travel in currents below sea level to the deepest parts of the ocean floor.
Secretion of calcium carbonate shells by reef-building organisms produce large quantities of limestone. Evaporation of seawater has resulted in the formation of widespread layers of salt and gypsum. Swamps rich in plants can produce coal if organic material accumulates and is buried before aerobic bacteria can destroy the dead plants. Sedimentary rocks are classified on the basis of the sizes of the particles in the rock and the composition of the rock.
Clastic sedimentary rocks comprise fragments of preexisting rocks and minerals. Chemical precipitates are sedimentary rocks that are made by precipitation of minerals from seawater, salt lakes, or mineral-rich springs. Organic sedimentary rocks formed from organic matter or organic activity, such as coal and limestone made by reef-building organisms like coral. Grain sizes in sedimentary rocks range from fine clay and silt to sand to boulders.
The sediment in a sedimentary rock reflects its environment of deposition. For example, wind-blown sand grains commonly is evidence of abrasion of their surfaces as a result of colliding with other grains. Sediments transported long distances tend to decrease in size and are more rounded than sediment deposited near their precursor rocks because of wearing against other sediments or rocks. Large or heavy sediments tend to wear out of water or wind if the energy of the water or wind is insufficient to carry the sediments.
Sediments deposited rapidly as a result of slides or slumps tend to include a larger range of sediment sizes, from large boulders to pebbles to sand grains and flakes of clay. Such rocks are called conglomerate. Along beaches, the rhythmic activity of waves moving sediment back and forth produces sandstones in which the grains are well rounded and of similar size. Glaciers pick up and carry a wide variety of sediments and often scratch or scrape the rocks over which they travel.
Sedimentary rocks are the only rocks in which fossils can be preserved because at the elevated temperatures and pressures in which igneous and metamorphic rocks form, fossils and organic remnants are ruined. The presence of fossils and the types of fossil organisms in a rock provide clues about the environment and age of sedimentary rocks. For example, fossils of human beings are not present in rocks older than approximately two million years because humans did not exist before then. Similarly, dinosaur fossils do not occur in rocks younger than about 65 million years because dinosaurs became extinct at that very time.
Fish fossils in sedimentary rock indicate that the sediments that make up the rock were deposited in a lake, river, or marine environment. By establishing the environment of the fossils in a rock, scientists learn more about the conditions under which the rock formed.
Spectacular exposures of sedimentary rocks include the Grand Canyon which is in Arizona, the eolian sandstones of Zion National Park which is in Utah, the limestones of Carlsbad National Park which is in New Mexico, and glacial features of Voyageurs National Park which is in Minnesota. Metamorphic rocks are named for the process of change that affects rocks. The changes that make metamorphic rocks usually include rises in the temperature (generally to 392°F) and the pressure of a precursor rock, which can be igneous, sedimentary, or metamorphic, to a degree that the minerals in the rock are no longer stable. The rock might change in mineral content or appearance, or even both. Clues to identifying metamorphic rocks include the presence of minerals such as mica, amphibole, staurolite, and garnet, and layers in which minerals are aligned as a result of pressure applied to the rock.
Common metamorphic rocks include slate, schist, and gneiss. Metamorphic rocks commonly are made in mountains such as the Appalachian Mountains, parts of California, and the ancient, eroded metamorphic rocks in the Llano Uplift of central Texas. Metamorphic rocks are classified depending on their constituent minerals and texture. Foliated metamorphic rocks are those that have a layered texture. In foliated metamorphic rocks, elongate or platy minerals such as mica and amphibole become aligned as a result of pressure on the rock. Foliation can range from alternating layers of light and dark minerals typical of gneiss to the seemingly perfect alignment of platy minerals in slate.
Some metamorphic rocks aren’t foliated and have a massive texture devoid of layers. Mineralogy of metamorphic rocks reflects the mineral content of the precursor rock and the pressure and temperature at which metamorphism occurs. As sediments undergo metamorphism, the layers of sediment can be folded or become more pronounced as pressure on the rock increases. Elongate or platy minerals in the rock tend to become aligned in the same direction.
For example, when shale metamorphoses to slate, it becomes easier to split the well-aligned layers of the slate into thin, flat sheets. This property of slate makes it an attractive roofing material. Marble-metamorphosed limestone typically does not have the pronounced layers of slate, but is used for flooring and sculptures.
Metamorphism of igneous rocks can cause the different minerals in the rocks to separate into layers. When granite metamorphoses into gneiss, layers of light-colored minerals and dark-colored minerals form. As with sedimentary rocks, elongate or platy minerals become well-aligned as pressure on the rock increases.
As sediments undergo metamorphism, the layers of sediment can be folded or become more pronounced as pressure on the rock increases. Elongate or platy minerals in the rock tend to become aligned in the same direction. For example, when shale metamorphoses to slate, it becomes easier to split the well-aligned layers of the slate into thin, flat sheets. This property of slate makes it an attractive roofing material.
Marble-metamorphosed limestone-typically does not have the pronounced layers of slate, but is used for flooring and sculptures. Metamorphism of igneous rocks can cause the different minerals in the rocks to separate into layers. When granite metamorphoses into gneiss, layers of light-colored minerals and dark-colored minerals are made. As with sedimentary rocks, elongate or platy minerals become well-aligned as pressure on the rock increases.
It is possible for metamorphic rocks to change into other metamorphic rocks. In some regions, especially areas where mountain building is taking place, it is not unusual for several episodes of change to affect rocks. It can be difficult to unravel the effects of each episode of metamorphism. The word igneous comes from the Latin word ignis which means of fire. Sedimentary rocks make layers at the bottoms of oceans and lakes.
Hi there! My mother, Camilla suggested that I write a series of posts about birds on my blog since I’ve been talking about them and learning about them. Please let me know if you have any bird books, CDs, or a website you’d recommend! Here is the part about Mountain Blue Birds.
Mountain Bluebirds are moderately small thrushes with round heads and straight, thin bills. Compared with other bluebirds they are slender and long-winged, with a long tail. Male Mountain Bluebirds are sky-blue, a little bit darker on the wings and the tail and a little bit paler on the belly, with white up under the tail. Females are pretty much gray-brown with tints of pale blue in the wings and the tail.
They occasionally show orange-brown throughout the chest. Mountain Bluebirds’ bills are completely black. Younger Mountain Bluebirds have fewer spots than the other young of little bluebirds. Unlike other bluebird species, Mountain Bluebirds often hover while foraging; they also pounce on their insect prey from an higher perch.
In the winter, the species often occur in large flocks wandering the landscape eating on berries, particularly some of those junipers. Mountain Bluebirds are mostly common in the West’s wide-open spaces, particularly at middle and higher elevations like mountains. They breed in native habitats such as prairie, sagebrush steppe, and even alpine tundra; anywhere with open country with at least a few trees that can provide nest cavities. They also readily take to human-altered habitats, often nesting in bluebird boxes and foraging in pastures.
The powder-blue male Mountain Bluebird is among the most beautiful birds of the West. Living in more open terrain than the other two bluebirds, this species may nest in holes in cliffs or dirt banks when tree hollows are not available. It often seeks its food by hovering low over the grass in open fields. They lay 5 to 6 eggs, sometimes 4 to 8 eggs.
Pale blue, unmarked (occasionally white) are their colors. Incubation is by female for about 13 to 17 days. Young birds: Both parents feed nestlings. Young birds leave the nest about 17 to 23 days after hatching, and are protected by their parents for another 3 to 4 weeks.
They have 2 breeds each year. Mountain Bluebirds feed heavily on insects, including beetles, grasshoppers, caterpillars, crickets, ants, bees, and others. They also eat some berries, including those of mistletoe, hackberry, and other plants. Berries are very important in their diet in the wintertime.
Sometimes interbreeds with the Eastern Bluebird where their ranges overlap. Nest: Apparently the female selects the site for the nest. The site is in a cavity, usually a natural hollow or old woodpecker hole in tree, or in a birdhouse. Sometimes nests in holes in dirt banks, crevices in cliffs or among rocks, holes in sides of buildings, old nests of other birds (such as Cliff Swallow or Dipper).
Nest in cavity (probably built by both genders) is a loose cup of weed stems, grass, twigs, rootlets, pine needles, and maybe even lined with animal hair or animal feathers. Mountain bluebirds migrate relatively late in the fall and early in the spring. Winter range varies from year to year, depending on the food supplies. Flocks sometimes wander east on the Great Plains, and lonely stray birds occasionally go as far as the Atlantic Coast.
The mountain bluebird is six to seven inches in length. The mountain bluebird breeds from east-central Alaska, southern Yukon and western Manitoba, south in the mountains to southern California, central and southeastern Nevada, northern and east-central Arizona, southern New Mexico and east to northeastern North Dakota, western South Dakota and central Oklahoma. In winters, the birds go from Oregon south to Baja California, Mexico and southern Texas, and east to eastern Kansas, western Oklahoma and central Texas. The males or females arrive at the breeding site first.
The mountain bluebird breeds in high mountain meadows with scattered trees and bushes and short grass. In winters, they live at lower elevations in plains and grasslands. The lovely mountain bluebird (Sialia arctcia) was made the official state bird of Idaho in 1931. The male mountain bluebird is a brilliant sky-blue, the female is gray with blue on her wings and tail.
The bluebird family is especially common in Idaho’s mountains. Idaho recognizes two bird symbols; the peregrine falcon is the official state raptor. The mountain bluebird is currently the state bird of Nevada. The Mountain Bluebird has a large range, estimated globally at 4,400,000 square kilometers.
Native to Canada, the United States, and Mexico, the mountain bluebirds prefer grassland, forest, and shrubland ecosystems. The global population of this bird is estimated at 5,200,000 individuals and does not show signs of decline that would necessitate inclusion on the IUCN Red List. For this reason, the current evaluation status of the Mountain Bluebird is Least Concern. The Mountain Bluebird is most likely to be confused with other bluebirds.
Male Mountain Bluebirds lack any reddish coloration on their underparts unlike Eastern and Western Bluebirds. Females are more difficult to separate. Eastern Bluebirds have a brownish throat and white belly while Mountain Bluebirds have gray throats and bellies. Western Bluebirds are browner on the breast than Mountain Bluebirds and have thicker bills.
Male Mountain Bluebirds might be confused with other all blue birds like Indigo Buntings and Blue Grosbeaks but these birds have much thicker, conical bills.