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Sebago Granite
The Sebago Granite is a Carboniferous aged granite that appears in southern Maine. The formation covers around 400 square kilometers in area, and intruded into the surrounding rock approximately 325 million years ago. Location The Sebago Granite is a geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ... that makes up the Sebago Pluton (or the Sebago Granite Pluton) that appears mainly throughout southern Maine, near the Sebago Lake region. It is also considered to be part of the New Hampshire Plutonic Suites, and partly extends into New Hampshire. Composition This Sebago Granite is a 2-mica granite, and is mainly composed of potassium feldspar, quartz, biotite, and muscovite. Its composition is homogeneous in nature with fine to medium grain sizes. The propor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferous'' means "coal-bearing", from the Latin '' carbō'' ("coal") and '' ferō'' ("bear, carry"), and refers to the many coal beds formed globally during that time. The first of the modern 'system' names, it was coined by geologists William Conybeare and William Phillips in 1822, based on a study of the British rock succession. The Carboniferous is often treated in North America as two geological periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial animal life was well established by the Carboniferous Period. Tetrapods (four limbed vertebrates), which had originated from lobe-finned fish during the preceding Devonian, became pentadactylous in and diversified during the Carboniferous, including early amphibian line ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granite
Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground. It is common in the continental crust of Earth, where it is found in igneous intrusions. These range in size from dikes only a few centimeters across to batholiths exposed over hundreds of square kilometers. Granite is typical of a larger family of ''granitic rocks'', or ''granitoids'', that are composed mostly of coarse-grained quartz and feldspars in varying proportions. These rocks are classified by the relative percentages of quartz, alkali feldspar, and plagioclase (the QAPF classification), with true granite representing granitic rocks rich in quartz and alkali feldspar. Most granitic rocks also contain mica or amphibole minerals, though a few (known as leucogranites) contain almost no dark minerals. Granite is nearly alway ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geology Of Maine
The geology of Maine is part of the broader geology of New England and eastern North America. Geologic history Maine's geologic past is unknown prior to 650 million years ago, although some geologists have suggested that rocks over a billion years old may be present in units of the Chain Lakes in northwestern Maine. The state is made up of three distinct terranes, including Laurentia, Iapetus Ocean terranes and the former microcontinent of Avalonia. With the breakup of the supercontinent Pannotia beginning 600 million years ago, the new continent of Laurentia—Proto-North America—began shedding eroded material out into the newly formed Iapetus Ocean. The region experienced limestone and marine sediment deposition, in connection with the erosion of a neighboring microcontinent. The region that is now northern Penobscot Bay, which then belonged to the microcontinent Avalonia, experienced an episode of pegmatite intrusion and metamorphism around 650 million years ago. Thro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geological Formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by Abraham Gottlob Wer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pluton
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey; the Henry Mountains of Utah; the Bushveld Igneous Complex of South Africa; Shiprock in New Mexico; the Ardnamurchan intrusion in Scotland; and the Sierra Nevada Batholith of California. Because the solid country rock into which magma intrudes is an excellent insulator, cooling of the magma is extremely slow, and intrusive igneous rock is coarse-grained (phaneritic). Intrusive igneous rocks are classified separately from extrusive igneous rocks, generally on the basis of their mineral content. The relative amounts of quartz, alkali feldspar, plagioclase, and feldspathoid is particularly important in classifying intrusive igneous rocks. Intrusions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maine
Maine () is a state in the New England and Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and northwest, respectively. The largest state by total area in New England, Maine is the 12th-smallest by area, the 9th-least populous, the 13th-least densely populated, and the most rural of the 50 U.S. states. It is also the northeasternmost among the contiguous United States, the northernmost state east of the Great Lakes, the only state whose name consists of a single syllable, and the only state to border exactly one other U.S. state. Approximately half the area of Maine lies on each side of the 45th parallel north in latitude. The most populous city in Maine is Portland, while its capital is Augusta. Maine has traditionally been known for its jagged, rocky Atlantic Ocean and bayshore coastlines; smoothly contoured mountains; heavily f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sebago Lake
Sebago Lake is the deepest and second-largest lake in the U.S. state of Maine. The lake is deep at its deepest point, with a mean depth of . It is possible that Sebago is the deepest lake wholly contained within the entire New England region, although some sources say that Vermont's Lake Willoughby is slightly deeper. Sebago covers about in surface area, has a length of and has a shoreline length of roughly . The surface is around above sea level, so the deep bottom is below the present sea level. It is in Cumberland County, and bordered by the towns of Casco, Naples, Raymond, Sebago, Standish and Windham. The seasonally occupied town of Frye Island is on an island in the lake. Sebago Lake and the surrounding area is known for its erratic and sudden changes in weather during all seasons, likely due to its proximity to the Atlantic Ocean and to Mt. Washington, a very notorious extreme weather hotspot. The name comes from the Abenaki ''sobagoo'', meaning "it is the sea" o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weakly radioactive because all isotopes of uranium are unstable; the half-lives of its naturally occurring isotopes range between 159,200 years and 4.5 billion years. The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99% of uranium on Earth) and uranium-235 (which has 143 neutrons). Uranium has the highest atomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead, and slightly lower than that of gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite. In nature, uranium is found as uranium-238 (99. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cross-cutting Relationships
Cross-cutting relationships is a principle of geology that states that the geologic feature which cuts another is the younger of the two features. It is a relative dating technique in geology. It was first developed by Danish geological pioneer Nicholas Steno in ''Dissertationis prodromus'' (1669) and later formulated by James Hutton in ''Theory of the Earth'' (1795) and embellished upon by Charles Lyell in ''Principles of Geology'' (1830). Types There are several basic types of cross-cutting relationships: *Structural relationships may be faults or fractures cutting through an older rock. *Intrusional relationships occur when an igneous pluton or dike is intruded into pre-existing rocks. *Stratigraphic relationships may be an erosional surface (or unconformity) cuts across older rock layers, geological structures, or other geological features. *Sedimentological relationships occur where currents have eroded or scoured older sediment in a local area to produce, for example, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Migmatite
Migmatite is a composite rock found in medium and high-grade metamorphic environments, commonly within Precambrian cratonic blocks. It consists of two or more constituents often layered repetitively: one layer is an older metamorphic rock that was reconstituted subsequently by partial melting ("paleosome"), while the alternate layer has a pegmatitic, aplitic, granitic or generally plutonic appearance ("neosome"). Commonly, migmatites occur below deformed metamorphic rocks that represent the base of eroded mountain chains. Migmatites form under extreme temperature and pressure conditions during prograde metamorphism, when partial melting occurs in metamorphic paleosome. Components exsolved by partial melting are called neosome (meaning ‘new body’), which may or may not be heterogeneous at the microscopic to macroscopic scale. Migmatites often appear as tightly, incoherently folded veins ( ptygmatic folds).Recommendations by the IUGS Subcommission on the Systematics of M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pegmatite
A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite. However, rarer intermediate composition and mafic pegmatites are known. Many of the world's largest crystals are found within pegmatites. These include crystals of microcline, quartz, mica, spodumene, beryl, and tourmaline. Some individual crystals are over long. Most pegmatites are thought to form from the last fluid fraction of a large crystallizing magma body. This residual fluid is highly enriched in volatiles and trace elements, and its very low viscosity allows molecules to migrate rapidly to join an existing crystal rather than coming together to form new crystals. This allows a few very large crystals to form. While most pegmatites have a simple composition of minerals common in ordinary igneous rock, a few ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metasedimentary Rock
In geology, metasedimentary rock is a type of metamorphic rock. Such a rock was first formed through the deposition and solidification of sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an .... Then, the rock was buried underneath subsequent rock and was subjected to high pressures and temperatures, causing the rock to recrystallize. The overall composition of a metasedimentary rock can be used to identify the original sedimentary rock, even where they have been subject to high-grade metamorphism and intense deformation. Types of metasedimentary rocks See also * References Metamorphic petrology {{petrology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
