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Contour plots of the radial component of the magnetic field at the core–mantle boundary (a) for the year 1715 and (b) for 1980. The contour interval is 100 microteslas; solid-line contours represent flux into the core, and broken-line contours…

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from article Hydrological consequences of global warming

The hydrologic cycle is characterized by evaporation and transpiration from the surfaces; transport of water vapor in the atmosphere by the wind, clouds, and precipitation; and water storage in snow, glaciers, groundwater, and oceans. Units: 1000…

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from article Hydrological consequences of global warming

Spatial patterns of climate model projections of (a) precipitation, (b) soil moisture, (c) runoff, and (d) evaporation for 2090–2099 under the mid-range A1B emission scenario from the Intergovernmental Panel for Climate Change 2007. (Climate Change…

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from article Micrometeorology

Soundings of temperature versus height for (a) day time and (b) nighttime obtained by radiosonde measurements during the Wangara experiment near Hay, New South Wales, Australia, in 1967. Soundings are shown for 9 A.M. through 9 P.M. on day 33 of the…

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from article Micrometeorology

The 3 P.M. sounding from Fig. 1a showing the layers of the daytime convective boundary layer.

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from article Earth's heat flow

Geographic distribution of heat flow measurement sites. (After H. N. Pollack, S. J. Hurter, and J. R. Johnson, Heat flow from the Earth's interior: Analysis of the global data set, Rev. Geophys., 31(3):267–280, 1993)

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from article Earth's heat flow

Heat flow–versus–age relationships for continents and oceans. (After D. Sprague and H. N. Pollack, Heat flow in the Mesozoic and Cenozoic, Nature, 285:393–395, 1980)

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from article Earth's heat flow

Geographic distribution of 17 heat flow provinces where the linear relationship between measured heat flow and radiogenic heat production from near-surface rocks has been empirically determined. (After I. Vitorello and H. N. Pollack, On the…

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from article Earth's heat flow

Present-day global heat flow (degree 12 spherical harmonic representation). Contours are in milliwatts per square meter. (After H. N. Pollack, S. J. Hurter, and J. R. Johnson, Heat flow from the Earth's interior: Analysis of the global data set,…

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from article Chicxulub impact crater

Bouguer gravity anomaly map over the Chicxulub impact crater. The coastline is designated by a thin white line, cenotes (natural pits) and sinkholes are designated by black dots, and the city of Mérida and the town of Chicxulub Puerto are designated…

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from article Chicxulub impact crater

Seismic line imaging of what lies beneath the seafloor, showing the Chicxulub impact crater. The crater includes many faults that can be grouped into an exterior ring fault, a series of outer ring faults, and a series of inner ring faults. Within…

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from article Marine ecology

Cross-sectional profile of (a) estuarine and nearshore and (b) coastal and open-ocean marine environments. The nearshore region, although not precisely defined, is generally within kilometers of the coastline. 1 m = 3.3 ft.

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from article Marine ecology

Salinity structure of the three general types of estuaries found throughout the world. (a) Strongly stratified system due to high surface freshwater inflow. (b) Moderated stratified system showing lines of equal salinity in parts per thousand. (c)…

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from article Marine ecology

Photosynthetically active radiation intensity at depth for various values of the attenuation coefficient (k). The intersection of the 1% light level (the limiting light intensity for photosynthesis) with the decay curves marks the depth limit for…

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from article Marine ecology

Photosynthesis–photosynthetically active radiation curves for two marine plants with fundamentally different light relations. The high-light plant, which has a higher Pmax but requires much more light, is typical of high-light environments such as…

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from article Graptolithina

Sketches of portions of pterobranch and graptolite colonies showing the dwelling tubes and the constructional units of the graptolite skeleton. (a) Young Rhabdopleura compacta colony with founder zooid and first asexual bud (Recent). Benthic…

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from article Graptolithina

Scanning electron micrograph of a graptolite (Pseudoclimacograptus scharengergi) showing the fuselli (horizontal ridges) that compose graptolite thecae, and the cortical bandages (oblique strips) that were deposited on top of the fuselli (Middle…

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from article Graptolithina

Hypothetical form of zooids that inhabited colony tubes, based on a planktic graptolite. Large zooids are shown with possible oarlike swimming organs used to move the colony through the ocean water and tentacles for feeding. Also shown are two…

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from article Graptolithina

Examples of some planktic graptolites, reconstructed to show three-dimensional form.

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from article Plant vulnerability to climate change

Subarctic tundra and vegetation of the Denali National Park and Preserve in Alaska. As a result of climate change and the resultant poleward and upward shift of plant ranges, plants and their ecosystems may become particularly vulnerable. (Credit:…

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from article Plant vulnerability to climate change

Blue grama (Bouteloua gracilis) growing in Montana. As a result of warming temperatures, this type of grass could face decreased productivity, allowing forbs to increase and making the ecosystem less tolerant of drought and grazing. (Credit: Matt…

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from article Plant vulnerability to climate change

Modeled distribution of suitable climate space in Europe for stiff sedge (Carex bigelowii), which is an Arctic-Alpine plant: (a) during the period 1961–1990 (green color = suitable climate space during the 1961–1990 period); (b) climate model…

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from article Plant vulnerability to climate change

The endangered western prairie fringed orchid (Platanthera praeclara) is declining across much of its range in North America. (Credit: U.S. Fish and Wildlife Service)

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from article Geologic time scale

Geologic time scale. CLICK on image to enlarge. (Credit: International Commission on Stratigraphy, 2018)

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from article Geophysical exploration

Bouguer gravity of a portion of the Perth Basin, Western Australia. Contour interval is 1 milliGal; datum is arbitrary. Departures from regularity are called anomalies. The bulge A results from an uplift area, the contour offset along BB′ is an…

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from article Geophysical exploration

Variation of shape measurements across an anomaly. Among the shape factors sometimes measured are A, the distance over which the slope is maximum; B, the distance between points where the slope is half of the maximum slope; C, half the width of the…

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from article Geophysical exploration

Bending of seismic waves at interface; V2 > V1.

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from article Geophysical exploration

Wavefronts become more widely spaced and ray paths become curved as velocity increases with depth.

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from article Geophysical exploration

Measuring reflected seismic wave energy. (a) Dipping reflector. (b) Flat reflector.

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from article Geophysical exploration

Refractive seismic exploration data. (a) Section through model of layered earth. Curves (wavefronts) indicate location of seismic energy at successive times after a shot at A. Beyond B, energy traveling in the second layer arrives first; beyond C,…

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from article Geophysical exploration

Reflection of seismic energy obtained from reflection point R (common midpoint) by positioning a source at A and a detector at A′. The same point is involved with a source at B and a detector at B′, or C and C′. The redundancy in measuring…

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from article Geophysical exploration

Seismic surveying at sea is done by towing a long streamer containing detectors that sense seismic energy. Seismic energy is generated by several air guns that are also towed from the ship.

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from article Geophysical exploration

Seismic record section from the North Sea. The layer from about 2 to 2.3 s at the right edge is composed primarily of salt that has undergone plastic flow. The folding of the rock formations is attributed to this salt movement. The upfolding (an…

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from article Wulfenite

Wulfenite. (a) Thin tabular crystals on limonite, Organ Mountains, New Mexico (American Museum of Natural History specimen). (b) Crystal habits (after C. Klein and C. S. Hurlbut, Jr., Manual of Mineralogy, 21st ed., John Wiley and Sons, 1993).

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from article Palaeonisciformes

Mimia toombsi (Gardiner & Bartram, 1977), Late Devonian, Gogo, Australia. One of the earliest palaeonisciforms, reaching 15 cm (6 in.) long, and known by complete fossils. (Reprinted with permission from B. G. Gardiner, The relationships of the…

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from article Palaeonisciformes

Chirodus granulosus (Young, 1866) was a deep-bodied palaeonisciform that grew to 10 cm (4 in.) and lived in Carboniferous coal swamps of Britain. The teeth formed cutting blades that may have been used to crop vegetation. This reconstruction is…

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from article Continental margin

Continental margin off the northeastern United States.

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from article Continental margin

California continental borderland, showing the outlines of the major basins. Upwelling is centered in the area south of the northern Channel Islands and extends south to 33°N latitude. (After D. S. Gorsline, J. Sediment. Petrol., 48:1056, 1978)

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from article Continental margin

Deepwater gyre between the Gulf Stream and the North American continent, influencing continental shelf circulation. Georges Bank is at the center of the illustration, separating the Gulf of Maine from deep water, and is subject to intense tidal…

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from article Cladoselache

Cladoselache fyleri, from the Upper Devonian of Cleveland. (After S. E. Bendix-Algreen, 1975)

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from article Instrumented buoys

Atlas toroid buoy with its meteorological instrumentation. (Pacific Marine and Environmental Laboratory, NOAA)

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from article Instrumented buoys

RAFOS float showing the whole instrument, with a detail of the right end in the foreground. (Graduate School of Oceanography, University of Rhode Island)

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from article Instrumented buoys

An autonomous profiler float, PALACE type. (Webb Research Corp.)

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from article Petrography

Examples of petrographic features. Images b, c, and f are reflected light images; the crystal in f has been etched and coated with a reflective coating to reveal contrasts. Images d, e, g, h, and i are transmitted light images, all in plane…

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from article Dynamic instability

The vorticity of a fluid is related to the rate at which a rigid paddle wheel would rotate if placed in the flow. (a) The paddle wheel rotates because the velocity of the fluid varies in a direction perpendicular to the flow. (b) Rotation is…

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from article Dynamic instability

Diagram showing barotropic instability. (a) All of the vorticity of an idealized shear flow shown concentrated on a line. (b) Line envisaged as a row of individual vortices. If two vortices are displaced in the manner illustrated in b, the flow they…

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from article Dynamic instability

Schematic diagram showing the formation of a cyclone in the Northern Hemisphere. (a) A tongue of high-potential-vorticity air from the stratosphere extends downward and southward into the troposphere; this tongue induces a counterclockwise…

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from article Paleocopa

Paleocopa. (a) Ogmoopsis nodulifera, left valve; from the Ordovician of Sweden. (b) Eurychilina subradiata, right valve showing wide complete frill; Ordovician of Minnesota. (c) Sulcicuneus porrectinatium, male and female carapaces; Devonian of…

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from article Marine conservation

A marine conservation biologist surveying marine invertebrates in a Mediterranean marine protected area in the Gulf of Gökova, Turkey. (Credit: Images & Stories/Alamy Stock Photo)

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from article Marine conservation

Bleached Acropora coral in shallow water, French Polynesia. Warming climates have affected marine habitats, with numerous marine species being depleted, threatened, or endangered. (Credit: Seaphotoart/Alamy Stock Photo)

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