Glossary

Quartzite

Fact Sheet:

Chemical Composition: Primarily composed of quartz (SiO₂)
Hardness: 7 on the Mohs scale
Crystal System: Metamorphic rock, non-foliated
Color Varieties: White, gray, pink, red, yellow, blue, green, and purple
Major Localities: United States, Brazil, Norway, South Africa, India, and Canada
Common Uses: Construction material, decorative stone, countertops, road ballast, and architectural applications

Introduction: Quartzite is a hard, durable metamorphic rock primarily composed of quartz that forms from the recrystallization of sandstone under intense heat and pressure. This process transforms the original quartz grains in the sandstone into a dense, interlocking mosaic of quartz crystals. Quartzite’s ...

^EEvapotranspiration

Evapotranspiration is the combined process of evaporation of water from the Earth’s surface and the transpiration of water from plants. It plays a critical role in the hydrological cycle, influencing water availability, soil moisture, and climate. Understanding evapotranspiration is essential for water resource management, agriculture, and climate modeling.

Reference: Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). “Crop Evapotranspiration: Guidelines for Computing Crop Water Requirements.” FAO Irrigation and Drainage Paper 56.

^EExfoliation

Exfoliation is a physical weathering process where rock layers peel away in sheets or slabs, often due to the release of pressure as overlying materials are removed. This process is common in large, homogeneous rock masses like granite, forming characteristic dome-shaped landforms. Exfoliation is significant in geomorphology and the study of weathering processes.

Reference: Twidale, C. R. (1982). “Granite Landforms.” Elsevier.

^EExhalative Deposits

Exhalative deposits are mineral deposits formed from the precipitation of minerals from hydrothermal fluids that are expelled onto the seafloor, typically associated with volcanic activity. These deposits are important in understanding the formation of massive sulfide deposits and other hydrothermal ore deposits.

Reference: Franklin, J. M., Gibson, H. L., Jonasson, I. R., & Galley, A. G. (2005). “Volcanogenic Massive Sulfide Deposits.” Economic Geology 100th Anniversary Volume, 523-560.

^EExhumation (Geology)

Exhumation in geology refers to the process by which rocks that were once buried deep within the Earth’s crust are brought to the surface through erosion, tectonic uplift, or other geological processes. This process is crucial for exposing deep-seated rocks, such as those formed under high pressure and temperature conditions, and for understanding the tectonic history of a region.

Reference: Ring, U., Brandon, M. T., Willett, S. D., & Lister, G. S. (1999). “Exhumation Processes: Normal Faulting, Ductile Flow and Erosion.” Geological Society, London, Special Publications, 154(1), 1-27.

^EExotic Terrane

An exotic terrane is a fragment of crustal material that has been transported and accreted onto a continent, typically as a result of plate tectonic processes. These terranes often have a different geological history and composition compared to the surrounding crust, providing valuable insights into the processes of continental growth and the tectonic evolution of regions.

Reference: Coney, P. J., Jones, D. L., & Monger, J. W. H. (1980). “Cordilleran Suspect Terranes.” Nature, 288(5789), 329-333.

^EExsolution

Exsolution is the process by which a solid solution separates into two or more distinct phases, typically as a result of cooling. This process is common in minerals such as feldspar and pyroxene, where exsolution can lead to the formation of lamellae or other fine-scale structures. Exsolution is important in mineralogy and petrology for understanding the thermal history of rocks and the evolution of mineral compositions.

Reference: Smith, J. V., & Brown, W. L. (1988). “Feldspar Minerals.” Springer.

^EExtrusion (Geology)

Extrusion refers to the process by which magma reaches the Earth’s surface and solidifies to form volcanic rocks. The study of extrusion processes is important in understanding volcanic activity, the formation of volcanic landforms, and the petrology of extrusive rocks.

Reference: Williams, H., Turner, F. J., & Gilbert, C. M. (1982). “Petrography: An Introduction to the Study of Rocks in Thin Sections.” W. H. Freeman.

^EExtrusive Rock

Extrusive rock, or volcanic rock, forms from magma that erupts onto the Earth’s surface and cools rapidly, resulting in fine-grained textures. Examples include basalt, andesite, and rhyolite. Extrusive rocks are important in the study of volcanology, plate tectonics, and the interpretation of past volcanic activity.

Reference: Winter, J. D. (2010). “Principles of Igneous and Metamorphic Petrology.” Pearson.

^FFacies

A facies refers to a body of rock with specific characteristics that distinguish it from adjacent rock units, typically reflecting particular conditions of deposition, such as environment, energy level, and sediment supply. Facies analysis is crucial in sedimentology, stratigraphy, and paleoenvironmental reconstruction, helping geologists interpret past depositional environments and changes over time.

Reference: Walker, R. G., & James, N. P. (1992). Facies Models: Response to Sea Level Change. Geological Association of Canada.

^FFacies Model

A facies model is a conceptual framework used to interpret and predict the distribution of sedimentary facies within a depositional environment. These models help geologists understand the processes that control sediment deposition and the spatial relationships between different sedimentary units. Facies models are crucial in sedimentology, stratigraphy, and petroleum geology.

Reference: Walker, R. G., & James, N. P. (1992). Facies Models: Response to Sea Level Change. Geological Association of Canada.

^FFault

A fault is a fracture or zone of fractures in the Earth’s crust along which movement has occurred. Faults can range in size from a few centimeters to thousands of kilometers and are categorized into types such as normal, reverse, and strike-slip based on the direction of movement. Faults are significant in understanding tectonic processes, earthquake generation, and the structural evolution of the Earth’s crust.

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

^FFault Bend Fold

A fault bend fold is a type of fold that forms as a layer of rock is deformed by movement along a fault with a bend or step in its trajectory. These folds are important in structural geology, providing insights into the deformation of the Earth’s crust and the mechanics of fault-related structures.

Reference: Suppe, J. (1983). Geometry and Kinematics of Fault-Bend Folding. American Journal of Science.

^FFault Block

A fault block is a large section of the Earth’s crust that has been displaced and rotated along a fault or set of faults. These blocks can be uplifted or downthrown, leading to the formation of mountain ranges, basins, and other large-scale geological features. Fault blocks are significant in tectonics, structural geology, and the study of crustal deformation.

Reference: Davis, G. H., & Reynolds, S. J. (1996). Structural Geology of Rocks and Regions. John Wiley & Sons.

^FFault Breccia

Fault breccia is a type of rock formed within a fault zone, composed of angular fragments of rock that have been crushed and broken by fault movement. These fragments are typically cemented together by finer materials. Fault breccia is significant in the study of fault mechanics, rock deformation, and the interpretation of past seismic activity.

Reference: Sibson, R. H. (1977). Fault Rocks and Fault Mechanisms. Journal of the Geological Society.

^FFault Gouge

Fault gouge is a fine-grained, unconsolidated material found within a fault zone, formed by the grinding and crushing of rocks during fault movement. It can affect the mechanical properties of faults, including frictional resistance and permeability. Fault gouge is important in the study of fault mechanics, earthquake behavior, and the evolution of fault zones.

Reference: Chester, F. M., & Logan, J. M. (1986). Implications for Mechanical Properties of Brittle Faults from Observations of the Punchbowl Fault Zone, California. Pure and Applied Geophysics.

^FFault Plane

A fault plane is the flat or gently curved surface along which there is slip during an earthquake or faulting event. The orientation and characteristics of the fault plane are critical in understanding the nature of the fault, the movement of the Earth’s crust, and the generation of earthquakes.

Reference: Scholz, C. H. (2002). The Mechanics of Earthquakes and Faulting. Cambridge University Press.

^FFault Trench

A fault trench is an excavation made across a fault to study its structure, history, and movement. Trenching is commonly used in paleoseismology to identify past earthquake events and assess seismic hazards. Fault trenches reveal the stratigraphy and deformation patterns associated with faulting.

Reference: McCalpin, J. P. (2009). Paleoseismology. Elsevier.

^FFelsic Rock

Felsic rock is a type of igneous rock that is rich in silica and light-colored minerals, such as quartz, feldspar, and muscovite. Examples include granite and rhyolite. Felsic rocks are important in understanding the evolution of continental crust and the processes of magmatic differentiation.

Reference: Best, M. G. (2003). Igneous and Metamorphic Petrology. Wiley-Blackwell.

^FFissile

Fissile refers to a rock’s ability to be easily split along closely spaced planes, typically due to the alignment of platy minerals or the presence of bedding or cleavage. Fissile rocks, such as shale, are important in understanding sedimentary structures, stratigraphy, and the mechanical behavior of rocks under stress.

Reference: Tucker, M. E. (2003). Sedimentary Rocks in the Field: A Practical Guide. Wiley-Blackwell.

^FFissure Eruption

A fissure eruption occurs when magma rises through cracks or fissures in the Earth’s crust, rather than through a central vent, leading to the formation of long, linear volcanic features. These eruptions can produce extensive lava flows and are often associated with rift zones or large igneous provinces. Fissure eruptions are significant in understanding volcanic processes and the formation of basaltic plateaus.

Reference: Thordarson, T., & Self, S. (1993). The Laki (Skaftár Fires) and Grímsvötn Eruptions in 1783–1785. Bulletin of Volcanology.

^FFjord

A fjord is a long, narrow, deep inlet of the sea between high cliffs or steep slopes, created by the submergence of a glaciated valley. Fjords are significant features in the study of glacial geomorphology, providing insights into past glacial activity, sea level changes, and the interaction between glaciers and coastal environments.

Reference: Syvitski, J. P. M., & Shaw, J. (1995). Sedimentology and Geomorphology of Fjords. Elsevier.

^FFlint

Flint is a hard, sedimentary form of the mineral quartz, usually found as nodules in chalk or limestone. Flint has been historically important as a tool-making material, particularly in the Stone Age. Its study provides insights into prehistoric technology, sedimentary environments, and the processes of diagenesis.

Reference: Pettijohn, F. J. (1975). Sedimentary Rocks. Harper & Row.

^FFlocculation

Flocculation is the process by which fine particles in suspension aggregate to form larger particles or flocs, typically due to the action of chemical agents or changes in water chemistry. This process is important in sedimentation, water treatment, and the study of fine-grained sediment transport in rivers, lakes, and oceans.

Reference: Van Olphen, H. (1977). An Introduction to Clay Colloid Chemistry. Wiley-Interscience.

^VArchives: Glossary

Volcanic gases are the volatile components released from magma during an eruption, including water vapor, carbon dioxide, sulfur dioxide, hydrogen sulfide, and other trace gases. These gases are significant in volcanology for understanding eruption dynamics, the impact of volcanic eruptions on the atmosphere, and the monitoring of volcanic activity.

Reference: Symonds, R. B., Gerlach, T. M., & Reed, M. H. (2001). “Magmatic Gas Scrubbing: Implications for Volcano Monitoring.” Journal of Volcanology and Geothermal Research, 108(1-4), 1-4.