Glossary

Pyroxene

Fact Sheet:

Chemical Composition: General formula XY(Si, Al)₂O₆, where X can be calcium (Ca), sodium (Na), iron (Fe²⁺), or magnesium (Mg), and Y is typically magnesium (Mg), iron (Fe), or aluminum (Al)
Hardness: 5 to 7 on the Mohs scale
Crystal System: Monoclinic or orthorhombic
Color Varieties: Green, black, brown, white, yellow, and dark gray
Major Localities: United States, Italy, Norway, Australia, Canada, and Japan
Common Uses: Rock-forming mineral in igneous and metamorphic rocks, ceramics, and geological research

Introduction: Pyroxene is a group of important rock-forming minerals found in many igneous and metamorphic rocks. Characterized by their ...

^NNormal Polarity

Normal polarity refers to the orientation of the Earth’s magnetic field in the same direction as the present magnetic field, where the magnetic north pole is near the geographic north pole. This concept is important in paleomagnetism for understanding the history of Earth’s magnetic field and the process of geomagnetic reversals.

Reference: Butler, R. F. (1992). “Paleomagnetism: Magnetic Domains to Geologic Terranes.” Blackwell Science.

^NNunatak

A nunatak is a mountain peak or rocky ridge that protrudes above a glacier or ice sheet. Nunataks are significant as they provide evidence of past glaciation, serve as refuges for plant and animal species during glacial periods, and are important markers in studying glacial dynamics.

Reference: Sugden, D. E., & John, B. S. (1976). “Glaciers and Landscape: A Geomorphological Approach.” Edward Arnold.

^OOblate Spheroid

An oblate spheroid is a shape that is flattened at the poles and bulging at the equator, describing the approximate shape of the Earth due to its rotation. This concept is important in geodesy, the study of Earth’s shape, gravity field, and rotational dynamics.

Reference: Heiskanen, W. A., & Moritz, H. (1967). “Physical Geodesy.” Freeman.

^OOcean Trench

An ocean trench is a deep, elongated depression in the ocean floor, typically formed at convergent plate boundaries where one tectonic plate is subducted beneath another. Ocean trenches are the deepest parts of the ocean and are significant for studying subduction zones, the recycling of oceanic crust, and the dynamics of plate tectonics.

Reference: Stern, R. J. (2002). “Subduction Zones.” Reviews of Geophysics, 40(4), 3-1-3-38.

^OOceanic Crust

The oceanic crust is the outermost layer of the Earth’s lithosphere that underlies the ocean basins. It is composed primarily of basalt, gabbro, and other mafic rocks, and is thinner but denser than continental crust. The study of oceanic crust is essential for understanding plate tectonics, seafloor spreading, and the geodynamic processes of the Earth’s mantle.

Reference: White, R. S., & McKenzie, D. (1989). “Magmatism at Rift Zones: The Generation of Volcanic Continental Margins and Flood Basalts.” Journal of Geophysical Research, 94(B6), 7685-7729.

^OOceanic Plateau

An oceanic plateau is a large, relatively flat region of the ocean floor that is elevated above the surrounding seafloor, often formed by large-scale volcanic activity. These plateaus are significant for understanding the processes of mantle plumes, hotspot volcanism, and the formation of large igneous provinces.

Reference: Coffin, M. F., & Eldholm, O. (1994). “Large Igneous Provinces: Crustal Structure, Dimensions, and External Consequences.” Reviews of Geophysics, 32(1), 1-36.

^OOffshore Bar

An offshore bar is a submerged or partly exposed ridge of sand, gravel, or other sediment that lies parallel to the shore and is formed by the action of waves and currents. Offshore bars are important for understanding coastal processes, sediment transport, and the dynamics of beach and shoreline systems.

Reference: Komar, P. D. (1998). “Beach Processes and Sedimentation.” Prentice Hall.

^OOffshore Drilling

Offshore drilling is the process of extracting oil and natural gas from beneath the ocean floor using specialized drilling rigs and platforms. This technique is significant for the global energy industry, the exploration of marine hydrocarbon reserves, and the environmental challenges associated with drilling in marine environments.

Reference: Holland, P. (2014). “Offshore Oil and Gas Exploration: Background, Challenges, and Future Development.” Springer.

^OOnlap

Onlap refers to the progressive covering of older strata by younger sedimentary layers that lap onto an inclined surface or structure. This process is important in sequence stratigraphy for interpreting changes in sea level, sediment supply, and the depositional environment over time.

Reference: Catuneanu, O. (2006). “Principles of Sequence Stratigraphy.” Elsevier.

^OOolite

Oolite is a sedimentary rock formed from ooids, which are small, spherical grains composed of concentric layers of calcium carbonate or other minerals. Oolites are typically found in warm, shallow marine environments and are significant in the study of carbonate sedimentation and paleoenvironmental reconstruction.

Reference: Tucker, M. E., & Wright, V. P. (1990). “Carbonate Sedimentology.” Blackwell Science.

^OOphiolite

Ophiolites are sections of the Earth’s oceanic crust and upper mantle that have been uplifted and exposed above sea level, typically as a result of tectonic processes such as obduction. These rock complexes provide valuable insights into the composition and structure of the oceanic crust, as well as the processes of seafloor spreading and subduction.

Reference: Moores, E. M., & Vine, F. J. (1971). “The Troodos Massif, Cyprus, and Other Ophiolites as Oceanic Crust: Evaluation and Implications.” Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, 268(1192), 443-466.

^OOrogenic Belt

An orogenic belt is a region of the Earth’s crust that has been deformed and uplifted during an orogeny, resulting in the formation of mountain ranges. These belts are characterized by complex geological structures, including folds, faults, and metamorphic rocks, and are important for understanding the tectonic evolution of continents.

Reference: Hatcher, R. D. (1989). “Tectonics of the Southern and Central Appalachian Internides.” Annual Review of Earth and Planetary Sciences, 17, 251-283.

^OOrogenic Collapse

Orogenic collapse refers to the process by which mountain ranges formed during orogeny are subsequently thinned and lowered by extensional tectonics and gravitational forces. This process is significant for understanding the post-orogenic evolution of mountain belts, crustal thinning, and the formation of extensional basins.

Reference: Dewey, J. F. (1988). “Extensional Collapse of Orogens.” Tectonics, 7(6), 1123-1139.

^OOrogenic Gold

Orogenic gold deposits are formed during orogeny, typically within metamorphic belts where gold is concentrated by hydrothermal fluids. These deposits are significant for gold exploration and understanding the processes of mineralization associated with tectonic activity.

Reference: Groves, D. I., Goldfarb, R. J., Robert, F., & Hart, C. J. R. (2003). “Gold Deposits in Metamorphic Belts: Overview of Current Understanding, Outstanding Problems, Future Research, and Exploration Significance.” Economic Geology, 98(1), 1-29.

^OOrogenic Plateau

An orogenic plateau is a high-elevation, relatively flat region formed during orogeny, typically associated with large-scale tectonic uplift and crustal thickening. Examples include the Tibetan Plateau, which is the result of the collision between the Indian and Eurasian plates. These plateaus are important for understanding the processes of mountain building, climate interactions, and the evolution of large orogenic systems.

Reference: Tapponnier, P., et al. (2001). “Oblique Stepwise Rise and Growth of the Tibet Plateau.” Science, 294(5547), 1671-1677.

^OOrogeny

Orogeny refers to the process of mountain building through tectonic forces, including the folding, faulting, and uplift of the Earth’s crust. Orogenies result from the collision of tectonic plates and are significant in the formation of mountain ranges, such as the Himalayas and the Andes. Understanding orogeny is crucial for studying the Earth’s tectonic history and the structural evolution of continents.

Reference: Dewey, J. F., & Bird, J. M. (1970). “Mountain Belts and the New Global Tectonics.” Journal of Geophysical Research, 75(14), 2625-2647.

^PPahoehoe

Pahoehoe is a type of basaltic lava with a smooth, ropy surface, formed by the slow cooling and movement of fluid lava. This type of lava flow is significant for understanding volcanic processes, particularly the behavior of low-viscosity basaltic lavas during effusive eruptions.

Reference: Macdonald, G. A. (1972). “Volcanoes.” Prentice Hall.

^PPaleochannel

A paleochannel is an ancient, inactive river or stream channel that has been filled or buried by younger sediments. These channels are important for reconstructing past drainage patterns, sedimentary environments, and the history of fluvial systems, as well as for locating potential reservoirs of groundwater or hydrocarbons.

Reference: Bridge, J. S. (2003). “Rivers and Floodplains: Forms, Processes, and Sedimentary Record.” Blackwell Science.

^PPaleoclimatology

Paleoclimatology is the study of past climates using evidence found in tree rings, ice cores, sediment layers, and other geological and biological records. This field is critical for understanding the natural variability of Earth’s climate, the causes of past climate changes, and their impacts on the environment and human societies.
Reference: Bradley, R. S. (1999). “Paleoclimatology: Reconstructing Climates of the Quaternary.” Academic Press.

^PPaleocurrent Analysis

Paleocurrent analysis is the study of the direction of ancient water or wind currents based on the orientation of sedimentary structures such as cross-bedding, ripple marks, and flute casts. This analysis is important for reconstructing paleoenvironments, sediment transport pathways, and the depositional history of sedimentary basins.

Reference: Potter, P. E., & Pettijohn, F. J. (1977). “Paleocurrents and Basin Analysis.” Springer-Verlag.

^PPaleogene Period

The Paleogene Period is a division of the geological timescale that lasted from about 66 to 23 million years ago, following the extinction of the dinosaurs. This period is significant for the diversification of mammals, the development of modern plant species, and the establishment of many of the Earth’s current ecosystems.

Reference: Berggren, W. A., & Pearson, P. N. (2005). “A Revised Tropical to Subtropical Paleogene Planktonic Foraminiferal Zonation.” Journal of Foraminiferal Research, 35(4), 279-298.

^PPaleomagnetism

Paleomagnetism is the study of the record of the Earth’s magnetic field preserved in rocks, sediments, and archaeological materials. This field of study is important for understanding plate tectonics, the movement of continents, and the history of the Earth’s magnetic field, including geomagnetic reversals.

Reference: Butler, R. F. (1992). “Paleomagnetism: Magnetic Domains to Geologic Terranes.” Blackwell Science.

^PPaleosol

A paleosol is a fossil soil, preserved in the geological record, that formed on a landscape surface in the past. Paleosols are important for reconstructing past climates, vegetation, and landscapes, as well as for understanding soil development and diagenetic processes over geological time scales.

Reference: Retallack, G. J. (2001). “Soils of the Past: An Introduction to Paleopedology.” Wiley-Blackwell.

^SArchives: Glossary

Subduction-related volcanism occurs when an oceanic plate is forced under a continental or another oceanic plate, leading to the melting of the subducted plate and the formation of volcanic arcs. This type of volcanism is significant for understanding the geochemical evolution of magmas and the hazards associated with explosive eruptions.

Reference: Turner, S., & Hawkesworth, C. (1998). “The Role of the Subduction Zone in Magmatism.” Journal of Geophysical Research: Solid Earth, 103(B1), 819-835.

Rocks

Glossary

N

Normal Polarity

N

Nunatak

O

Oblate Spheroid

O

Ocean Trench

O

Oceanic Crust

O

Oceanic Plateau

O

Offshore Bar

O

Offshore Drilling

O

Onlap

O

Oolite

O

Ophiolite

O

Orogenic Belt

O

Orogenic Collapse

O

Orogenic Gold

O

Orogenic Plateau

O

Orogeny

P

Pahoehoe

P

Paleochannel

P

Paleoclimatology

P

Paleocurrent Analysis

P

Paleogene Period

P

Paleomagnetism

P

Paleosol

Pyroxene

NNormal Polarity

NNunatak

OOblate Spheroid

OOcean Trench

OOceanic Crust

OOceanic Plateau

OOffshore Bar

OOffshore Drilling

OOnlap

OOolite

OOphiolite

OOrogenic Belt

OOrogenic Collapse

OOrogenic Gold

OOrogenic Plateau

OOrogeny

PPahoehoe

PPaleochannel

PPaleoclimatology

PPaleocurrent Analysis

PPaleogene Period

PPaleomagnetism

PPaleosol

SArchives: Glossary