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Calcite concretion formed in Paleocene marine siltstone, Moeraki beach, New Zealand. Uncemented siltstone has been eroded away by wave action. Concretion is about 2 m (7 ft) in diameter, which is unusually large.

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from article Authigenic minerals

Scanning electron micrograph of authigenic kaolinite. The clay mineral formed from dissolution of calcic feldspar in a Miocene sandstone, San Joaquin basin, California.

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from article Authigenic minerals

Scanning electron micrograph of clinoptilolite zeolite (white crystals) on smectite-coated (dark background) sand grains. Sample is from Paleocene volcanic sandstone, Baja California, Mexico.

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from article Barracuda

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from article Engineering geology

Diagram of a typical landslide monitoring instrumentation. (Credit: USGS)

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from article Engineering geology

Rock-physics laboratory instrumentation for testing triaxial shear strength. Shearing stresses tend to separate portions of the rock (or soil) mass. Faults and folds are examples of shear failures in nature. In engineering structures, every…

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from article Engineering geology

Geologic map that can be used to identify geologic hazards and for land-use planning. (Credit: USGS)

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from article Sequence stratigraphy

Seismic reflection characterization. (a) Seismic transect across the western margin of Bimini Bank, Bahamas Platform, showing variations in seismic facies. Note the poorly reflective rocks at lower right, representing a sedimentary basement bounded…

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from article Sequence stratigraphy

Clastic-dominated sequence. (a) Model for clastic-dominated sequences on an extensional continental margin, showing the key stratigraphic surfaces and the four major systems tracts that develop within each sequence. Double-headed arrows show three…

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from article Cartography

Paper and smartphone maps for navigation. (Credit: Mmaxer/Shutterstock)

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from article Cartography

Distribution of chronic wasting disease of the deer family in North America, April 2018. (Credit: Bryan Richards, USGS National Wildlife Health Center)

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from article Cartography

Computer rendering of the topography of the 48 contiguous United States based on 12 million elevations. (USGS)

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from article Electric filter

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from article Electric filter

Passive, lumped-element filters. (a) RC low-pass filter. (b) LC band-pass filter.

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from article Electric filter

Ladder structure. (a) Overall structure with alternating series and shunt arms. (b) LC circuit whose impedance contains both a finite-frequency pole and a zero. Such circuits are used in the series and shunt arms of the ladder structure.

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from article Electric filter

Mechanical filter.

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from article Electric filter

Single-amplifier filters. (a) Low-pass Sallen-Key filter. (b) Low-pass, infinite-gain, single-amplifier filter. (c) Cascade of second-order filter realizations.

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from article Electric filter

Multiple-amplifier filters. (a) State-variable (KHN) filter. (b) Tow-Thomas filter.

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from article Electric filter

Simulated-inductor realization of fifth-order high-pass filter. (a) RLC prototype, normalized for cutoff frequency of 1 rad/s (0.159 Hz). (b) Direct active-RC realization.

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from article Satellite television broadcasting

Direct broadcasting television satellite system.

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from article Xenophyophorida

Xenophyophorids. (a) Stannoma dendroides. (b) Stannophyllum zonarium. (c) Psammetta erythrocytomorpha, section showing interlacing tubules and dark inclusions of uncertain nature.

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from article Oolite

Plain light micrographs of thin sections of ooids and pisoids. (a) Oolite of Mississippian age, southwestern Indiana. (b) Pisoids from the hot springs of Karlovy Vary (Carlsbad), Czech Republic. The lower right pisoid shows a rock fragment nucleus…

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from article Atmospheric tides

Variation of tidal amplitudes with height. The shaded area shows the general range of solar diurnal and semidiurnal amplitudes (on a logarithmic scale) as a function of height. The line corresponds to amplitude varying inversely with the square root…

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from article Musk-ox

Musk-ox (Ovibos moschatus). (Credit: Brent Huffman/Ultimate Ungulate Images)

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from article Marten

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from article Human ecology

Shacks and garbage along a dirty river in a slum in Manila, Philippines. Human ecology encompasses how individual people and their communities interact with their particular environment. In many cases, though, humans have created polluted…

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from article Human ecology

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from article Igneous rock

Some plutonic rock names and their volcanic equivalents.

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from article Igneous rock

IUGS classifications of gabbroic rocks (triangle AQP) and ultramafic rocks (triangle AFP). (From A. Streckeisen, To each plutonic rock its proper name, Earth Sci. Rev., 12:1–33, 1976)

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from article Igneous rock

Photomicrographs of common igneous rock textures. (a) Hypidiomorphic-granular texture. (b) Porphyritic texture. (c) Pyroclastic texture. Width of field of view is 3.2 mm (0.125 in.).

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from article Igneous rock

Photomicrographs of some mineral textures in igneous rocks. (a) Poikilitic texture in alkali feldspar. (b) Perthitic texture in alkali feldspar. (c) Zoned texture in plagioclase. Width of field of view is 3.2 mm (0.125 in.).

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from article Igneous rock

Some volcanic structures. (a) Lava plateau with flat-lying basalt lava flows, near Sprague, Washington. (b) Composite volcanoes, Atitlan (left) and Toliman in Guatemala. (c) Columnar jointing in andesite near Lost Creek Dam, Oregon. (d) Pillow…

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from article Igneous rock

Some plutonic structures.

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from article Phyllite

Shiny folded phyllite with mica crystals too small to be seen with the naked eye. (Credit: Stephen Reynolds)

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from article Tanaidacea

Leviapseudes bipartitus. [K. Larsen, Deep-Sea Tanaidacea (Peracarida) from the Gulf of Mexico, Brill, Leiden, 2005]

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from article Tanaidacea

Typhlotanais ohtsukae: (top) female; (bottom) male. [K. Larsen and M. Shimomura, Tanaidacea (Crustacea: Peracarida) from Japan: II. Tanaidomorpha from the East China Sea, the West Pacific Ocean and the Nansei Islands, Zootaxa, 1464:1–43, 2007]

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from article Rock mechanics

Typical rock mass containing numerous discontinuities. The person in picture is conducting a scanline survey, where a tape is placed across the rock and detailed information is gathered on the fractures that intersect the scanline.

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from article Rock mechanics

(a) Uniaxial compression test, where an axial stress is applied to a core sample of rock and increased until failure. (b) Triaxial compression test, where a constant confining stress is first applied, then the axial stress is increased until failure.

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from article Rock mechanics

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from article Rock mechanics

(a) Example of the failure zone around an underground excavation (×, shear failure; o, tensile failure), calculated using the Rocscience Phase2 computer program. (b) Example of a shallow underground excavation where the failure mode is either…

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from article Rock mechanics

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from article Cassiduloida

Major features of cassiduloids as shown on a test of Cassidulus caribaearum (a Caribbean species) with spines (upper two figures) and without spines (lower two figures). Top (aboral) views are shown on the left; bottom (oral) views are shown on the…

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from article Rhynchosauria

Skull (dorsal view) of the rhynchosaur Paradapedon.

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from article Protist

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from article Chrysocolla

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from article Atmospheric acoustics

Frequency dependence of attenuation coefficient in units of decibels per 100 m (dB/328 ft), temperature of 20°C (68°F), and a relative humidity of 70%. Total attenuation from air absorption and contributions from classical absorption (that due to…

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from article Atmospheric acoustics

Diagram of reflection of sound from a flat ground surface with impedance Z, showing direct (R1) and reflected (R2) paths from source to receiver, source height hs, microphone height h, distance of propagation d, and angle of incidence or grazing…

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from article Atmospheric acoustics

Relative sound pressure levels (SPL) for propagation from a source over mown grass for source height of 1.8 m (6 ft), microphone height of 1.5 m (5 ft), and distances of propagation indicated.

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from article Atmospheric acoustics

Curved ray paths. (a) Refraction downward, during temperature inversion or downwind propagation. (b) Refraction upward, during temperature lapse or upwind propagation.

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from article Atmospheric acoustics

Representative long-range ray paths of sound radiating from a source in the atmosphere and traveling from west to east in Northern Hemisphere in winter. 1 km = 0.6 mi. (After T. F. Malone, ed., Compendium of Meteorology, American Meteorological…

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