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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 Blowpipe

Glassblower blowing into a blowpipe to shape molten glass. (Credit: Hero Images/Getty Images)

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from article Tin

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from article Tin

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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 Isoelectric point

Titration of alanine with sodium hydroxide (NaOH), showing the course of pH with added fractional equivalents. The four arrows show, from left to right, the pKa [½ cations: NH3+(CH3)COOH, and ½ zwitterions: NH3+(CH3)CHCOO−], the pl (all…

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from article Isoelectric point

Course of the charges carried by lysine (pKa = 2.18) molecules in dilute aqueous solution with pH during a titration with alkali. Shown are the net charge, going from +2 at low pH to +1 between pH 4.5 and 6.5, the isoelectric point at pH 9.74, the…

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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 Sloan Digital Sky Survey

Sloan Digital Sky Survey (SDSS) 2.5-m (98-in.) telescope at Apache Point Observatory, New Mexico. The secondary mirror is visible in the center of the aperture. The square structure surrounding the primary and secondary mirrors shelters them from…

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from article Sloan Digital Sky Survey

Spectrum of a galaxy (image inset) receding at around 6000 km s−1 (3700 mi s−1), or about 2% of the speed of light. The vertical line shows the wavelength at which one expects to observe the emission line Hα for an object at rest (656.3 nm). The…

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from article Sloan Digital Sky Survey

Distribution of galaxies within 4° of the celestial equator from the SDSS. In this polar plot, the radius indicates the distance from the Milky Way, and the angle is the right ascension. The diameter shown is 8 × 109 light-years. Blank areas have…

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from article Sloan Digital Sky Survey

Map of stars in the SDSS. Grayscale signifies density of stars on the sky. Several streams of stars are noticeable. Areas in background are those unobserved by the survey. (Courtesy of Vasily Belokurov; Sloan Digital Sky Survey)

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from article Sloan Digital Sky Survey