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86-410: The mission of MERC is to conduct and promote cutting-edge, field-based, collaborative research on mineral deposits and their environments, and to educate and train highly qualified personnel (HQP) for careers in the minerals industry, academia or government. The objectives of MERC are to: 1) promote collaborative university-government-industry research on mineral deposits and Precambrian geology, 2) pursue

172-535: A characteristic fabric . All three types may melt again, and when this happens, new magma is formed, from which an igneous rock may once again solidify. Organic matter, such as coal, bitumen, oil, and natural gas, is linked mainly to organic-rich sedimentary rocks. To study all three types of rock, geologists evaluate the minerals of which they are composed and their other physical properties, such as texture and fabric . Geologists also study unlithified materials (referred to as superficial deposits ) that lie above

258-484: A magnetosphere around a planet. Early space probes discovered the gross dimensions of the terrestrial magnetic field, which extends about 10 Earth radii towards the Sun. The solar wind , a stream of charged particles, streams out and around the terrestrial magnetic field, and continues behind the magnetic tail, hundreds of Earth radii downstream. Inside the magnetosphere, there are relatively dense regions of solar wind particles,

344-485: A petrographic microscope , where the minerals can be identified through their different properties in plane-polarized and cross-polarized light, including their birefringence , pleochroism , twinning , and interference properties with a conoscopic lens . In the electron microprobe, individual locations are analyzed for their exact chemical compositions and variation in composition within individual crystals. Stable and radioactive isotope studies provide insight into

430-554: A PhD in Mineral Exploration and Precambrian geology. MERC has managed a wide range of applied research projects, including numerous NSERC Natural Science and Engineering Research Council Collaborative Research and Development program projects and CAMIRO Canada Mining Industry Research Organization projects; managed the $ 8m Ontario Mineral Exploration Technology (OMET) program for the Ministry of Northern Development of Mines ; led

516-434: A definite homogeneous chemical composition and an ordered atomic arrangement. Each mineral has distinct physical properties, and there are many tests to determine each of them. Minerals are often identified through these tests. The specimens can be tested for: A rock is any naturally occurring solid mass or aggregate of minerals or mineraloids . Most research in geology is associated with the study of rocks, as they provide

602-665: A fundamental understanding of mineral deposits and their geological settings, 3) aid the mining industry in the discovery of ore deposits, and 4) train geologists in mineral exploration research techniques. MERC has research expertise in the geology , mineralogy , geochemistry , and genesis of magmatic nickel-copper-PGE deposits , volcanology , geochemistry, and alteration associated with hydrothermal copper-zine-(gold) volcanogenic massive sulfide ore deposits , structure, geochemistry, and alteration associated with hydrothermal orogenic lode gold deposits , mineralogy, geochemistry, and genesis of rare-element and rare-metal pegmatites , and

688-623: A length of less than a meter. Rocks at the depth to be ductilely stretched are often also metamorphosed. These stretched rocks can also pinch into lenses, known as boudins , after the French word for "sausage" because of their visual similarity. Where rock units slide past one another, strike-slip faults develop in shallow regions, and become shear zones at deeper depths where the rocks deform ductilely. The addition of new rock units, both depositionally and intrusively, often occurs during deformation. Faulting and other deformational processes result in

774-502: A major component of the $ 14m Discover Abitibi program for the [[Timmins Economic Development Corporation], Kirkland Lake Department of Economic Development and Tourism , Northern Ontario Heritage Fund Corporation , and FedNor ; is presently leading the $ 13m Mineral Exploration Footprints project funded by the [Natural Sciences and Engineering Research Council of Canada]] and the Canada Mining Innovation Council ; and

860-448: A means to provide information about geological history and the timing of geological events. The principle of uniformitarianism states that the geological processes observed in operation that modify the Earth's crust at present have worked in much the same way over geological time. A fundamental principle of geology advanced by the 18th-century Scottish physician and geologist James Hutton

946-415: A mountain as tall as, for example, 15 km (9 mi), would develop so much pressure at its base, due to gravity, that the rock there would become plastic , and the mountain would slump back to a height of roughly 10 km (6 mi) in a geologically insignificant time. Some or all of these geologic principles can be applied to other planets besides Earth. For instance on Mars, whose surface gravity

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1032-608: A number of fields, laboratory, and numerical modeling methods to decipher Earth history and to understand the processes that occur on and inside the Earth. In typical geological investigations, geologists use primary information related to petrology (the study of rocks), stratigraphy (the study of sedimentary layers), and structural geology (the study of positions of rock units and their deformation). In many cases, geologists also study modern soils, rivers , landscapes , and glaciers ; investigate past and current life and biogeochemical pathways, and use geophysical methods to investigate

1118-451: A sedimentary rock. Sedimentary rocks are mainly divided into four categories: sandstone, shale, carbonate, and evaporite. This group of classifications focuses partly on the size of sedimentary particles (sandstone and shale), and partly on mineralogy and formation processes (carbonation and evaporation). Igneous and sedimentary rocks can then be turned into metamorphic rocks by heat and pressure that change its mineral content, resulting in

1204-493: A single environment and do not necessarily occur in a single order. The Hawaiian Islands , for example, consist almost entirely of layered basaltic lava flows. The sedimentary sequences of the mid-continental United States and the Grand Canyon in the southwestern United States contain almost-undeformed stacks of sedimentary rocks that have remained in place since Cambrian time. Other areas are much more geologically complex. In

1290-441: A smooth and polished surface" suggested that it and other worlds might appear "just like the face of the Earth itself". Advances in telescope construction and instrumental resolution gradually allowed increased identification of the atmospheric as well as surface details of the planets. The Moon was initially the most heavily studied, due to its proximity to the Earth, as it always exhibited elaborate features on its surface, and

1376-400: A variety of applications. Dating of lava and volcanic ash layers found within a stratigraphic sequence can provide absolute age data for sedimentary rock units that do not contain radioactive isotopes and calibrate relative dating techniques. These methods can also be used to determine ages of pluton emplacement. Thermochemical techniques can be used to determine temperature profiles within

1462-555: A wide range of peer reviewed journals . Some planetary scientists work at private research centres and often initiate partnership research tasks. The history of planetary science may be said to have begun with the Ancient Greek philosopher Democritus , who is reported by Hippolytus as saying The ordered worlds are boundless and differ in size, and that in some there is neither sun nor moon, but that in others, both are greater than with us, and yet with others more in number. And that

1548-422: Is accomplished in two primary ways: through faulting and folding . In the shallow crust, where brittle deformation can occur, thrust faults form, which causes the deeper rock to move on top of the shallower rock. Because deeper rock is often older, as noted by the principle of superposition , this can result in older rocks moving on top of younger ones. Movement along faults can result in folding, either because

1634-642: Is an important transitional zone between the solid planetary surface and the higher rarefied ionizing and radiation belts. Not all planets have atmospheres: their existence depends on the mass of the planet, and the planet's distance from the Sun ;– too distant and frozen atmospheres occur. Besides the four giant planets , three of the four terrestrial planets ( Earth , Venus , and Mars ) have significant atmospheres. Two moons have significant atmospheres: Saturn 's moon Titan and Neptune 's moon Triton . A tenuous atmosphere exists around Mercury . The effects of

1720-460: Is an intimate coupling between the movement of the plates on the surface and the convection of the mantle (that is, the heat transfer caused by the slow movement of ductile mantle rock). Thus, oceanic parts of plates and the adjoining mantle convection currents always move in the same direction – because the oceanic lithosphere is actually the rigid upper thermal boundary layer of the convecting mantle. This coupling between rigid plates moving on

1806-433: Is horizontal). The principle of superposition states that a sedimentary rock layer in a tectonically undisturbed sequence is younger than the one beneath it and older than the one above it. Logically a younger layer cannot slip beneath a layer previously deposited. This principle allows sedimentary layers to be viewed as a form of the vertical timeline, a partial or complete record of the time elapsed from deposition of

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1892-616: Is important for mineral and hydrocarbon exploration and exploitation, evaluating water resources , understanding natural hazards , remediating environmental problems, and providing insights into past climate change . Geology is a major academic discipline , and it is central to geological engineering and plays an important role in geotechnical engineering . The majority of geological data comes from research on solid Earth materials. Meteorites and other extraterrestrial natural materials are also studied by geological methods. Minerals are naturally occurring elements and compounds with

1978-497: Is much less, the largest volcano, Olympus Mons , is 27 km (17 mi) high at its peak, a height that could not be maintained on Earth. The Earth geoid is essentially the figure of the Earth abstracted from its topographic features. Therefore, the Mars geoid ( areoid ) is essentially the figure of Mars abstracted from its topographic features. Surveying and mapping are two important fields of application of geodesy. An atmosphere

2064-488: Is presently conducting the $ 104m Metal Earth project funded by the Canada First Research Excellence Fund , FedNor , Northern Ontario Heritage Fund Corporation , and several industry sponsors. Geology Geology (from Ancient Greek γῆ ( gê )  'earth' and λoγία ( -logía )  'study of, discourse') is a branch of natural science concerned with

2150-478: Is primarily accomplished through normal faulting and through the ductile stretching and thinning. Normal faults drop rock units that are higher below those that are lower. This typically results in younger units ending up below older units. Stretching of units can result in their thinning. In fact, at one location within the Maria Fold and Thrust Belt , the entire sedimentary sequence of the Grand Canyon appears over

2236-568: Is that "the present is the key to the past." In Hutton's words: "the past history of our globe must be explained by what can be seen to be happening now." The principle of intrusive relationships concerns crosscutting intrusions. In geology, when an igneous intrusion cuts across a formation of sedimentary rock , it can be determined that the igneous intrusion is younger than the sedimentary rock. Different types of intrusions include stocks, laccoliths , batholiths , sills and dikes . The principle of cross-cutting relationships pertains to

2322-518: Is to demonstrate the age of the Earth . Geology provides evidence for plate tectonics , the evolutionary history of life , and the Earth's past climates . Geologists broadly study the properties and processes of Earth and other terrestrial planets. Geologists use a wide variety of methods to understand the Earth's structure and evolution, including fieldwork , rock description , geophysical techniques , chemical analysis , physical experiments , and numerical modelling . In practical terms, geology

2408-523: Is used for geologically young materials containing organic carbon . The geology of an area changes through time as rock units are deposited and inserted, and deformational processes alter their shapes and locations. Rock units are first emplaced either by deposition onto the surface or intrusion into the overlying rock . Deposition can occur when sediments settle onto the surface of the Earth and later lithify into sedimentary rock, or when as volcanic material such as volcanic ash or lava flows blanket

2494-641: The Apollo astronauts for the field geology they would encounter on their lunar missions. Overlapping sequences were identified on images taken by the Lunar Orbiter program , and these were used to prepare a lunar stratigraphic column and geological map of the Moon. One of the main problems when generating hypotheses on the formation and evolution of objects in the Solar System is the lack of samples that can be analyzed in

2580-498: The HED meteorites back to a specific asteroid in the main belt, 4 Vesta . The comparatively few known Martian meteorites have provided insight into the geochemical composition of the Martian crust, although the unavoidable lack of information about their points of origin on the diverse Martian surface has meant that they do not provide more detailed constraints on theories of the evolution of

2666-672: The Solar System ) and the processes of their formation. It studies objects ranging in size from micrometeoroids to gas giants , with the aim of determining their composition, dynamics, formation, interrelations and history. It is a strongly interdisciplinary field, which originally grew from astronomy and Earth science , and now incorporates many disciplines, including planetary geology , cosmochemistry , atmospheric science , physics , oceanography , hydrology , theoretical planetary science , glaciology , and exoplanetology . Allied disciplines include space physics , when concerned with

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2752-647: The Van Allen radiation belts . Planetary geophysics includes, but is not limited to, seismology and tectonophysics , geophysical fluid dynamics , mineral physics , geodynamics , mathematical geophysics , and geophysical surveying . Planetary geodesy (also known as planetary geodetics) deals with the measurement and representation of the planets of the Solar System, their gravitational fields and geodynamic phenomena ( polar motion in three-dimensional, time-varying space). The science of geodesy has elements of both astrophysics and planetary sciences. The shape of

2838-500: The bedrock . This study is often known as Quaternary geology , after the Quaternary period of geologic history, which is the most recent period of geologic time. Magma is the original unlithified source of all igneous rocks . The active flow of molten rock is closely studied in volcanology , and igneous petrology aims to determine the history of igneous rocks from their original molten source to their final crystallization. In

2924-436: The biosphere , but those meteorites collected in the last few decades from Antarctica are almost entirely pristine. The different types of meteorites that originate from the asteroid belt cover almost all parts of the structure of differentiated bodies: meteorites even exist that come from the core-mantle boundary ( pallasites ). The combination of geochemistry and observational astronomy has also made it possible to trace

3010-512: The geochemical evolution of rock units. Petrologists can also use fluid inclusion data and perform high temperature and pressure physical experiments to understand the temperatures and pressures at which different mineral phases appear, and how they change through igneous and metamorphic processes. This research can be extrapolated to the field to understand metamorphic processes and the conditions of crystallization of igneous rocks. This work can also help to explain processes that occur within

3096-451: The gravity fields of the planets to be mapped. For example, in the 1970s, the gravity field disturbances above lunar maria were measured through lunar orbiters, which led to the discovery of concentrations of mass, mascons , beneath the Imbrium, Serenitatis, Crisium, Nectaris and Humorum basins. If a planet's magnetic field is sufficiently strong, its interaction with the solar wind forms

3182-402: The mantle below (separated within itself by seismic discontinuities at 410 and 660 kilometers), and the outer core and inner core below that. More recently, seismologists have been able to create detailed images of wave speeds inside the earth in the same way a doctor images a body in a CT scan . These images have led to a much more detailed view of the interior of the Earth, and have replaced

3268-399: The rotation rate of a planet about its axis can be seen in atmospheric streams and currents. Seen from space, these features show as bands and eddies in the cloud system and are particularly visible on Jupiter and Saturn. Exoplanetology studies exoplanets , the planets existing outside our Solar System . Until recently, the means of studying exoplanets have been extremely limited, but with

3354-440: The 1960s, it was discovered that the Earth's lithosphere , which includes the crust and rigid uppermost portion of the upper mantle , is separated into tectonic plates that move across the plastically deforming, solid, upper mantle, which is called the asthenosphere . This theory is supported by several types of observations, including seafloor spreading and the global distribution of mountain terrain and seismicity. There

3440-469: The Earth is to a large extent the result of its rotation, which causes its equatorial bulge , and the competition of geologic processes such as the collision of plates and of vulcanism , resisted by the Earth's gravity field. These principles can be applied to the solid surface of Earth ( orogeny ; Few mountains are higher than 10 km (6 mi), few deep sea trenches deeper than that because quite simply,

3526-437: The Earth and other astronomical objects , the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth sciences , including hydrology . It is integrated with Earth system science and planetary science . Geology describes the structure of the Earth on and beneath its surface and the processes that have shaped that structure. Geologists study

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3612-424: The Earth, such as subduction and magma chamber evolution. Structural geologists use microscopic analysis of oriented thin sections of geological samples to observe the fabric within the rocks, which gives information about strain within the crystalline structure of the rocks. They also plot and combine measurements of geological structures to better understand the orientations of faults and folds to reconstruct

3698-478: The Grand Canyon in the southwestern United States being a very visible example, the lower rock units were metamorphosed and deformed, and then deformation ended and the upper, undeformed units were deposited. Although any amount of rock emplacement and rock deformation can occur, and they can occur any number of times, these concepts provide a guide to understanding the geological history of an area. Geologists use

3784-506: The Martian lithosphere . As of July 24, 2013, 65 samples of Martian meteorites have been discovered on Earth. Many were found in either Antarctica or the Sahara Desert. During the Apollo era, in the Apollo program , 384 kilograms of lunar samples were collected and transported to the Earth, and three Soviet Luna robots also delivered regolith samples from the Moon. These samples provide

3870-532: The Middle East. The total mass of recognized lunar meteorites is close to 50 kg. Space probes made it possible to collect data in not only the visible light region but in other areas of the electromagnetic spectrum. The planets can be characterized by their force fields: gravity and their magnetic fields, which are studied through geophysics and space physics. Measuring the changes in acceleration experienced by spacecraft as they orbit has allowed fine details of

3956-475: The Solar System and extrasolar planetary systems. Observing exoplanets and determining their physical properties, exoplanetology , is a major area of research besides Solar System studies. Every planet has its own branch. In planetary science, the term geology is used in its broadest sense, to mean the study of the surface and interior parts of planets and moons, from their core to their magnetosphere. The best-known research topics of planetary geology deal with

4042-408: The Sun, or the geomorphology of the surfaces of the terrestrial planets, to give only a few examples. The main comparison that can be made is to features on the Earth, as it is much more accessible and allows a much greater range of measurements to be made. Earth analog studies are particularly common in planetary geology, geomorphology, and also in atmospheric science. The use of terrestrial analogs

4128-425: The astronomy and physics or Earth sciences departments of universities or research centres, though there are several purely planetary science institutes worldwide. Generally, planetary scientists study one of the Earth sciences , astronomy , astrophysics , geophysics , or physics at the graduate level and concentrate their research in planetary science disciplines. There are several major conferences each year, and

4214-537: The beginning of the 20th century, advancement in geological science was facilitated by the ability to obtain accurate absolute dates to geological events using radioactive isotopes and other methods. This changed the understanding of geological time. Previously, geologists could only use fossils and stratigraphic correlation to date sections of rock relative to one another. With isotopic dates, it became possible to assign absolute ages to rock units, and these absolute dates could be applied to fossil sequences in which there

4300-515: The creation of topographic gradients, causing material on the rock unit that is increasing in elevation to be eroded by hillslopes and channels. These sediments are deposited on the rock unit that is going down. Continual motion along the fault maintains the topographic gradient in spite of the movement of sediment and continues to create accommodation space for the material to deposit. Deformational events are often also associated with volcanism and igneous activity. Volcanic ashes and lavas accumulate on

4386-437: The crust, the uplift of mountain ranges, and paleo-topography. Fractionation of the lanthanide series elements is used to compute ages since rocks were removed from the mantle. Other methods are used for more recent events. Optically stimulated luminescence and cosmogenic radionuclide dating are used to date surfaces and/or erosion rates. Dendrochronology can also be used for the dating of landscapes. Radiocarbon dating

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4472-410: The current rate of innovation in research technology , exoplanetology has become a rapidly developing subfield of astronomy . Planetary science frequently makes use of the method of comparison to give a greater understanding of the object of study. This can involve comparing the dense atmospheres of Earth and Saturn's moon Titan , the evolution of outer Solar System objects at different distances from

4558-623: The effects of the Sun on the bodies of the Solar System, and astrobiology . There are interrelated observational and theoretical branches of planetary science. Observational research can involve combinations of space exploration , predominantly with robotic spacecraft missions using remote sensing , and comparative, experimental work in Earth-based laboratories . The theoretical component involves considerable computer simulation and mathematical modelling . Planetary scientists are generally located in

4644-570: The fault is a normal fault or a thrust fault . The principle of inclusions and components states that, with sedimentary rocks, if inclusions (or clasts ) are found in a formation, then the inclusions must be older than the formation that contains them. For example, in sedimentary rocks, it is common for gravel from an older formation to be ripped up and included in a newer layer. A similar situation with igneous rocks occurs when xenoliths are found. These foreign bodies are picked up as magma or lava flows, and are incorporated, later to cool in

4730-403: The faults are not planar or because rock layers are dragged along, forming drag folds as slip occurs along the fault. Deeper in the Earth, rocks behave plastically and fold instead of faulting. These folds can either be those where the material in the center of the fold buckles upwards, creating " antiforms ", or where it buckles downwards, creating " synforms ". If the tops of the rock units within

4816-472: The features on planetary surfaces and reconstructs the history of their formation, inferring the physical processes that acted on the surface. Planetary geomorphology includes the study of several classes of surface features: The history of a planetary surface can be deciphered by mapping features from top to bottom according to their deposition sequence , as first determined on terrestrial strata by Nicolas Steno . For example, stratigraphic mapping prepared

4902-483: The folds remain pointing upwards, they are called anticlines and synclines , respectively. If some of the units in the fold are facing downward, the structure is called an overturned anticline or syncline, and if all of the rock units are overturned or the correct up-direction is unknown, they are simply called by the most general terms, antiforms, and synforms. Even higher pressures and temperatures during horizontal shortening can cause both folding and metamorphism of

4988-404: The formation of faults and the age of the sequences through which they cut. Faults are younger than the rocks they cut; accordingly, if a fault is found that penetrates some formations but not those on top of it, then the formations that were cut are older than the fault, and the ones that are not cut must be younger than the fault. Finding the key bed in these situations may help determine whether

5074-401: The history of rock deformation in the area. In addition, they perform analog and numerical experiments of rock deformation in large and small settings. Planetary science Planetary science (or more rarely, planetology ) is the scientific study of planets (including Earth ), celestial bodies (such as moons , asteroids , comets ) and planetary systems (in particular those of

5160-423: The internal composition and structure of the Earth. Seismologists can use the arrival times of seismic waves to image the interior of the Earth. Early advances in this field showed the existence of a liquid outer core (where shear waves were not able to propagate) and a dense solid inner core . These advances led to the development of a layered model of the Earth, with a lithosphere (including crust) on top,

5246-408: The intervals between the ordered worlds are unequal, here more and there less, and that some increase, others flourish and others decay, and here they come into being and there they are eclipsed. But that they are destroyed by colliding with one another. And that some ordered worlds are bare of animals and plants and all water. In more modern times, planetary science began in astronomy, from studies of

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5332-403: The laboratory, where a large suite of tools are available, and the full body of knowledge derived from terrestrial geology can be brought to bear. Direct samples from the Moon, asteroids and Mars are present on Earth, removed from their parent bodies, and delivered as meteorites . Some of these have suffered contamination from the oxidising effect of Earth's atmosphere and the infiltration of

5418-459: The later end of the scale, it is marked by the present day (in the Holocene epoch ). The following five timelines show the geologic time scale to scale. The first shows the entire time from the formation of the Earth to the present, but this gives little space for the most recent eon. The second timeline shows an expanded view of the most recent eon. In a similar way, the most recent era is expanded in

5504-454: The lowest layer to deposition of the highest bed. The principle of faunal succession is based on the appearance of fossils in sedimentary rocks. As organisms exist during the same period throughout the world, their presence or (sometimes) absence provides a relative age of the formations where they appear. Based on principles that William Smith laid out almost a hundred years before the publication of Charles Darwin 's theory of evolution ,

5590-493: The mantle and show the crystallographic structures expected in the inner core of the Earth. The geological time scale encompasses the history of the Earth. It is bracketed at the earliest by the dates of the first Solar System material at 4.567 Ga (or 4.567 billion years ago) and the formation of the Earth at 4.54 Ga (4.54 billion years), which is the beginning of the Hadean eon  – a division of geological time. At

5676-405: The matrix. As a result, xenoliths are older than the rock that contains them. The principle of original horizontality states that the deposition of sediments occurs as essentially horizontal beds. Observation of modern marine and non-marine sediments in a wide variety of environments supports this generalization (although cross-bedding is inclined, the overall orientation of cross-bedded units

5762-418: The mineralogical composition of rocks in order to get insight into their history of formation. Geology determines the relative ages of rocks found at a given location; geochemistry (a branch of geology) determines their absolute ages . By combining various petrological, crystallographic, and paleontological tools, geologists are able to chronicle the geological history of the Earth as a whole. One aspect

5848-615: The most comprehensive record of the composition of any Solar System body besides the Earth. The numbers of lunar meteorites are growing quickly in the last few years – as of April 2008 there are 54 meteorites that have been officially classified as lunar. Eleven of these are from the US Antarctic meteorite collection, 6 are from the Japanese Antarctic meteorite collection and the other 37 are from hot desert localities in Africa, Australia, and

5934-559: The planetary bodies in the near vicinity of the Earth: the Moon , and the two neighboring planets: Venus and Mars . Of these, the Moon was studied first, using methods developed earlier on the Earth. Planetary geology focuses on celestial objects that exhibit a solid surface or have significant solid physical states as part of their structure. Planetary geology applies geology , geophysics and geochemistry to planetary bodies. Geomorphology studies

6020-413: The primary record of the majority of the geological history of the Earth. There are three major types of rock: igneous , sedimentary , and metamorphic . The rock cycle illustrates the relationships among them (see diagram). When a rock solidifies or crystallizes from melt ( magma or lava ), it is an igneous rock . This rock can be weathered and eroded , then redeposited and lithified into

6106-569: The principles of succession developed independently of evolutionary thought. The principle becomes quite complex, however, given the uncertainties of fossilization, localization of fossil types due to lateral changes in habitat ( facies change in sedimentary strata), and that not all fossils formed globally at the same time. Geologists also use methods to determine the absolute age of rock samples and geological events. These dates are useful on their own and may also be used in conjunction with relative dating methods or to calibrate relative methods. At

6192-467: The rate of new discoveries is very high, partly due to the large number of interplanetary spacecraft currently exploring the Solar System. Planetary science studies observational and theoretical astronomy, geology ( astrogeology ), atmospheric science , and an emerging subspecialty in planetary oceans , called planetary oceanography . This is both an observational and a theoretical science. Observational researchers are predominantly concerned with

6278-428: The rocks. This metamorphism causes changes in the mineral composition of the rocks; creates a foliation , or planar surface, that is related to mineral growth under stress. This can remove signs of the original textures of the rocks, such as bedding in sedimentary rocks, flow features of lavas , and crystal patterns in crystalline rocks . Extension causes the rock units as a whole to become longer and thinner. This

6364-478: The sedimentology of Mississippi Valley-type (MVT) Pb-Zn deposits and placer Au and U deposits. MERC and the Harquail School of Earth Sciences are a world-leaders in mineral deposits education, offering a Co-Op BSc in Mineral Exploration program, hosting the annual PDAC-sponsored Student-Industry Mineral Exploration Workshop, offering a fully modular ("block") Applied MSc degree in Mineral Exploration, and offering

6450-433: The simplified layered model with a much more dynamic model. Mineralogists have been able to use the pressure and temperature data from the seismic and modeling studies alongside knowledge of the elemental composition of the Earth to reproduce these conditions in experimental settings and measure changes within the crystal structure. These studies explain the chemical changes associated with the major seismic discontinuities in

6536-524: The southwestern United States, sedimentary, volcanic, and intrusive rocks have been metamorphosed, faulted, foliated, and folded. Even older rocks, such as the Acasta gneiss of the Slave craton in northwestern Canada , the oldest known rock in the world have been metamorphosed to the point where their origin is indiscernible without laboratory analysis. In addition, these processes can occur in stages. In many places,

6622-474: The study of the small bodies of the Solar System: those that are observed by telescopes, both optical and radio, so that characteristics of these bodies such as shape, spin, surface materials and weathering are determined, and the history of their formation and evolution can be understood. Theoretical planetary astronomy is concerned with dynamics : the application of the principles of celestial mechanics to

6708-550: The subsurface. Sub-specialities of geology may distinguish endogenous and exogenous geology. Geological field work varies depending on the task at hand. Typical fieldwork could consist of: In addition to identifying rocks in the field ( lithology ), petrologists identify rock samples in the laboratory. Two of the primary methods for identifying rocks in the laboratory are through optical microscopy and by using an electron microprobe . In an optical mineralogy analysis, petrologists analyze thin sections of rock samples using

6794-407: The surface of the Earth and the convecting mantle is called plate tectonics . The development of plate tectonics has provided a physical basis for many observations of the solid Earth . Long linear regions of geological features are explained as plate boundaries: Plate tectonics has provided a mechanism for Alfred Wegener 's theory of continental drift , in which the continents move across

6880-488: The surface of the Earth over geological time. They also provided a driving force for crustal deformation, and a new setting for the observations of structural geology. The power of the theory of plate tectonics lies in its ability to combine all of these observations into a single theory of how the lithosphere moves over the convecting mantle. Advances in seismology , computer modeling , and mineralogy and crystallography at high temperatures and pressures give insights into

6966-474: The surface, and igneous intrusions enter from below. Dikes , long, planar igneous intrusions, enter along cracks, and therefore often form in large numbers in areas that are being actively deformed. This can result in the emplacement of dike swarms , such as those that are observable across the Canadian shield, or rings of dikes around the lava tube of a volcano. All of these processes do not necessarily occur in

7052-742: The surface. Igneous intrusions such as batholiths , laccoliths , dikes , and sills , push upwards into the overlying rock, and crystallize as they intrude. After the initial sequence of rocks has been deposited, the rock units can be deformed and/or metamorphosed . Deformation typically occurs as a result of horizontal shortening, horizontal extension , or side-to-side ( strike-slip ) motion. These structural regimes broadly relate to convergent boundaries , divergent boundaries , and transform boundaries, respectively, between tectonic plates. When rock units are placed under horizontal compression , they shorten and become thicker. Because rock units, other than muds, do not significantly change in volume , this

7138-495: The technological improvements gradually produced more detailed lunar geological knowledge. In this scientific process, the main instruments were astronomical optical telescopes (and later radio telescopes ) and finally robotic exploratory spacecraft , such as space probes . The Solar System has now been relatively well-studied, and a good overall understanding of the formation and evolution of this planetary system exists. However, there are large numbers of unsolved questions, and

7224-407: The third timeline, the most recent period is expanded in the fourth timeline, and the most recent epoch is expanded in the fifth timeline. Horizontal scale is Millions of years (above timelines) / Thousands of years (below timeline) Epochs: Methods for relative dating were developed when geology first emerged as a natural science . Geologists still use the following principles today as

7310-409: The unresolved planets. In this sense, the original planetary astronomer would be Galileo , who discovered the four largest moons of Jupiter , the mountains on the Moon , and first observed the rings of Saturn , all objects of intense later study. Galileo's study of the lunar mountains in 1609 also began the study of extraterrestrial landscapes: his observation "that the Moon certainly does not possess

7396-615: Was datable material, converting the old relative ages into new absolute ages. For many geological applications, isotope ratios of radioactive elements are measured in minerals that give the amount of time that has passed since a rock passed through its particular closure temperature , the point at which different radiometric isotopes stop diffusing into and out of the crystal lattice . These are used in geochronologic and thermochronologic studies. Common methods include uranium–lead dating , potassium–argon dating , argon–argon dating and uranium–thorium dating . These methods are used for

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