Glossary

Magnetite

Fact Sheet:
– Chemical Composition: Fe₃O₄ (Iron(II,III) Oxide)
– Hardness: 5.5 to 6.5 on the Mohs scale
– Crystal System: Isometric
– Color Varieties: Black to brownish-black with a metallic luster
– Major Localities: Australia, Brazil, Canada, and the United States
– Common Uses: Iron ore, magnetic materials, and catalysts

Introduction: Magnetite is a fascinating mineral known for its strong magnetic properties, which are unique among naturally occurring minerals. Its name comes from Magnesia, a region in Greece where the mineral was first discovered. Beyond its magnetic allure, magnetite is a crucial iron ore and has various industrial applications.

Formation: ...

^GGossan

A gossan is an iron-rich, weathered, oxidized zone found at the surface above a sulfide mineral deposit. Gossans are significant in mineral exploration as indicators of underlying ore deposits, particularly in the search for copper, gold, and other valuable metals. They form through the oxidation of sulfide minerals and the leaching of soluble components.

Reference: Guilbert, J. M., & Park, C. F. (1986). The Geology of Ore Deposits. Waveland Press.

^GGraben

A graben is a depressed block of the Earth’s crust bordered by parallel faults, typically forming a rift valley or basin. Grabens are significant in understanding extensional tectonics, where the Earth’s crust is stretched and thinned. They are often associated with volcanic activity and the formation of basins that may host sedimentary deposits.

Reference: McClay, K. R. (1990). Extensional Fault Systems in Sedimentary Basins: A Review of the Geometry, Processes, and Evolution. In: Extensional Tectonics and Stratigraphy of the North Atlantic Margins. AAPG Memoir 46.

^GGrain Flow

Grain flow is a type of sedimentary process where loose, granular material moves downslope under the influence of gravity. This process typically occurs in environments such as dunes, beaches, and submarine slopes, forming structures like cross-bedding and graded bedding. Understanding grain flow is important in sedimentology and the interpretation of sedimentary structures.

Reference: Middleton, G. V., & Southard, J. B. (1984). Mechanics of Sediment Movement. SEPM Society for Sedimentary Geology.

^GGranitic Magma

Granitic magma is a type of felsic magma rich in silica and aluminum, typically forming granite upon solidification. This magma is often associated with continental crust and forms through processes such as partial melting, fractional crystallization, and magma mixing. Granitic magma is crucial in understanding the formation of continental crust and the processes of magmatic differentiation.

Reference: Pitcher, W. S. (1993). The Nature and Origin of Granite. Springer.

^GGravitational Collapse (Geology)

Gravitational collapse in geology refers to the process where a mountain range or orogen undergoes extension and thinning due to the gravitational potential energy built up during tectonic compression. This process can lead to the formation of extensional faults, metamorphic core complexes, and the redistribution of crustal material.

Reference: Dewey, J. F. (1988). Extensional Collapse of Orogens. Tectonics.

^GGreenstone Belt

A greenstone belt is a region of ancient, metamorphosed volcanic and sedimentary rocks, typically of Archean to Proterozoic age, often associated with significant mineral deposits such as gold and nickel. Greenstone belts are important in understanding the early Earth’s tectonics, the formation of the continental crust, and the processes of mineralization.

Reference: de Wit, M. J., & Ashwal, L. D. (1997). Greenstone Belts. Oxford Monographs on Geology and Geophysics.

^GGroundwater

Groundwater is the water found beneath the Earth’s surface in soil pore spaces and fractures of rock formations. It is a crucial component of the hydrological cycle and a vital resource for drinking water, agriculture, and industry. The study of groundwater involves hydrogeology, which focuses on the distribution, movement, and quality of water in the subsurface.

Reference: Freeze, R. A., & Cherry, J. A. (1979). Groundwater. Prentice Hall.

^GGuyot

A guyot, also known as a tablemount, is an underwater volcanic mountain with a flat top, usually found in deep ocean basins. Guyots are formed by volcanic activity and are later eroded to sea level, creating the flat summit. They are significant in studying the geological history of ocean basins, plate tectonics, and the evolution of volcanic islands.

Reference: Menard, H. W. (1984). Origin of Guyots: The Beheaded Volcanoes. Geological Society of America Bulletin.

^GGyre

A gyre is a large system of circulating ocean currents, driven by wind patterns and the Earth’s rotation (Coriolis effect). Major oceanic gyres play a crucial role in climate regulation, nutrient distribution, and the movement of marine debris. Understanding gyres is important in oceanography, climate science, and environmental studies.

Reference: Tomczak, M., & Godfrey, J. S. (1994). Regional Oceanography: An Introduction. Elsevier.

^HHabitat Fragmentation

Habitat fragmentation refers to the process by which large, contiguous habitats are broken into smaller, isolated patches due to human activities or natural events. This phenomenon impacts biodiversity, ecosystem health, and species survival, and is significant in conservation biology and land-use planning.

Reference: Fahrig, L. (2003). Effects of Habitat Fragmentation on Biodiversity. Annual Review of Ecology, Evolution, and Systematics, 34(1), 487-515.

^HHalf-Graben

A half-graben is a type of geological structure formed by extensional tectonics, where one side of a fault is down-dropped, creating a basin that is fault-bounded on one side. Half-grabens are significant in the study of rift systems, sedimentary basin development, and the tectonic evolution of extensional terrains.

Reference: McClay, K. R. (1990). Extensional Fault Systems in Sedimentary Basins: A Review of the Geometry, Processes, and Evolution. AAPG Memoir 46.

^HHanging Valley

A hanging valley is a tributary valley that is elevated above the main valley floor, often formed by glacial activity. As glaciers carve deep U-shaped valleys, smaller tributary glaciers create shallower valleys, which later become “hanging” when the glaciers retreat. Hanging valleys are important in studying glacial geomorphology and the evolution of mountain landscapes.

Reference: Benn, D. I., & Evans, D. J. A. (2010). Glaciers and Glaciation. Routledge.

^HHanging Wall

The hanging wall is the block of rock that lies above an inclined fault plane, as opposed to the footwall, which lies below the fault plane. The concept of hanging wall and footwall is essential in structural geology for describing and analyzing fault movements, especially in mining and petroleum geology.

Reference: Twiss, R. J., & Moores, E. M. (2007). Structural Geology. W. H. Freeman.

^HHeadward Erosion

Headward erosion is a process in which the upper part of a stream or river valley erodes back towards its source, effectively lengthening the river. This process is significant in understanding river dynamics, landscape evolution, and the development of drainage networks.

Reference: Ferguson, R. I., & Werritty, A. (1983). Headward Erosion in a Small Scottish Catchment. Earth Surface Processes and Landforms, 8(4), 391-395.

^HHemipelagic Sediment

Hemipelagic sediment refers to fine-grained sediments that accumulate on the continental slope and rise, primarily consisting of a mixture of terrigenous and pelagic materials. These sediments are significant in understanding sedimentary processes in marine environments and can provide insights into past climate conditions and ocean circulation patterns.

Reference: Carter, R. M., & McCave, I. N. (1997). Hemipelagic Sedimentation in the Deep Sea. In: Seilacher, A. (Ed.), Facies Models: Response to Sea Level Change. Geological Association of Canada.

^HHeterogeneity (Geology)

Heterogeneity in geology refers to the variation in physical and chemical properties within geological materials, such as rocks or soils. This variation can influence fluid flow, mechanical behavior, and geochemical reactions, and is significant in fields such as hydrogeology, petroleum geology, and environmental science.

Reference: Pine, W. J., & Park, C. F. (2004). Geological Heterogeneity and Its Implications for Fluid Flow. Hydrogeology Journal, 12(1), 26-39.

^HHolocene

The Holocene is the current geological epoch, beginning approximately 11,700 years ago after the last major ice age. It is characterized by the development of human civilizations, significant climate changes, and the rise of agriculture. The Holocene is crucial in studying recent geological processes, climate history, and human impact on the environment.

Reference: Walker, M. J. C., & Lowe, J. J. (2007). Quaternary Geology: A Stratigraphic Framework for Multidisciplinary Work. Geological Society, London, Special Publications, 242(1), 1-21.

^HHornito

A hornito is a small, conical volcanic structure formed by the extrusion of lava through cracks in a solidified lava flow, often resembling a small spatter cone. Hornitos are important in understanding volcanic activity, the dynamics of lava flows, and the features associated with effusive eruptions.

Reference: Parfitt, E. A., & Wilson, L. (2008). Fundamentals of Physical Volcanology. Blackwell Publishing.

^HHorst

A horst is an uplifted block of the Earth’s crust bounded by normal faults on either side, typically forming elevated regions such as mountain ranges or plateaus. Horsts are significant in understanding extensional tectonics, crustal deformation, and the formation of rift valleys.

Reference: Twiss, R. J., & Moores, E. M. (2007). Structural Geology. W. H. Freeman.

^HHot Spot (Geology)

A hot spot is a location on the Earth’s surface where a plume of hot mantle material rises, causing volcanic activity independent of tectonic plate boundaries. Hot spots can create volcanic island chains, such as the Hawaiian Islands, as the tectonic plate moves over the stationary plume. Studying hot spots helps geologists understand mantle convection, intraplate volcanism, and the formation of volcanic islands.

Reference: Wilson, J. T. (1963). A Possible Origin of the Hawaiian Islands. Canadian Journal of Physics, 41(6), 863-870.

^HHot Spring

A hot spring is a natural geothermal feature where groundwater is heated by the Earth’s internal heat and rises to the surface, often resulting in the formation of thermal pools. Hot springs are significant in geothermal energy, mineral deposition, and unique ecosystems that thrive in warm, mineral-rich waters.

Reference: Miller, D. M. (1984). Geothermal Energy from Hot Springs. Geothermal Resources Council Bulletin, 13(3), 51-56.

^HHumus

Humus is the dark, organic material in soil formed from the decomposition of plant and animal matter. It is essential for soil fertility, providing nutrients for plants and improving soil structure and moisture retention. Humus plays a crucial role in soil formation, agriculture, and the carbon cycle.

Reference: Brady, N. C., & Weil, R. R. (2008). The Nature and Properties of Soils. Pearson.

^HHyaloclastite

Hyaloclastite is a volcanic rock formed by the rapid cooling and fracturing of lava upon contact with water, typically during submarine or subglacial eruptions. This rock is composed of glassy fragments and is important in understanding volcanic processes in underwater or glaciated environments and the interactions between lava and water.

Reference: Fisher, R. V., & Schmincke, H.-U. (1984). Pyroclastic Rocks. Springer.

^UArchives: Glossary

Underthrusting occurs when one tectonic plate is forced beneath another, a process often associated with subduction zones. This geological phenomenon is significant for understanding plate tectonics, the formation of mountain ranges, and seismic activity related to convergent plate boundaries.

Reference: Suppe, J. (1985). “Principles of Structural Geology.” Prentice Hall.