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U.S. Geological Survey Open-File Report 2009-1151

Continuous Resistivity Profiling and Seismic-Reflection Data Collected in 2006 from the Potomac River Estuary, Virginia and Maryland


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alluvial    Related to loose sediment deposited by water in a non-marine setting.

anomalies    Unusually high or low values or patterns.

aquifer (surficial and confined)    A permeable water-bearing layer of sediment or rock; a confined aquifer is isolated from the ground surface by one or more low-permeability layers of sediment or rock, while a surficial or unconfined aquifer is not.


brackish    Slightly to moderately salty.


conductivity    The ability of a material or mixture to carry an electrical current.


delta    A deposit of sediments found at the mouth of a river or tidal inlet.

dipole    A pair of positive and negative charges separated by a small distance.

draft    A nautical term describing the depth of an object on a ship below the water surface, often the bottom or keel of the ship.


ebb-tidal    Related to the falling or outgoing part of the tidal cycle.

estuary    A body of water typically found where a river meets the ocean.

eutrophication    An increase in the concentration of dissolved nutrients in a water body that increases growth or algae, often to a harmful degree, and often caused by human influences.


geophysical    Relating to the application of surface or borehole measurements, often using sound or electrical energy, to determine or infer the subsurface properties of land and water bodies.

groundwater    Water located beneath the ground surface or sediment surface in pore spaces and fractures.


Holocene  The geological epoch that began approximately 12,000 years ago at the end of the last ice age.


incision    Erosion of a river into the sediments or rock underlying it, especially during periods of lowered sea level or rapid uplift of the land.

interpolated    Interpreted conditions between locations of measured data.

inversion    The process of working backwards from measured properties, such as electrical resistivity, to reconstruct the actual conditions that yielded the measurements.


Julian day    Day of the year measured from January 1, without regard to months.


linearized    Converted from an irregular or curved path into a straight line to simplify computations.

lowstand    The period of lowest relative sea level during an ice age caused by net movement of water from oceans to glaciers by evaporation and precipitation as snow.


nutrients    Chemicals that organisms needs to live and grow, especially dissolved forms of nitrogen in the case of estuaries.


paleochannels or paleovalleys    Depressions cut by rivers into underlying material during periods of lower sea level, and now submerged by rising sea level and often partially or fully buried by sediments.

peat    Organic-rich sediment deposited beneath wetlands.

physiography    The physical features of the Earth's surface, especially the slope and elevation.

Pleistocene    The geologic epoch characterized by cycles of glaciation beginning 2.6 million years ago and ending approximately 12,000 years ago.

port    A nautical term for the left side of a ship when facing toward the front (bow).

potential    The property of electrical potential energy divided by electrical charge, usually measured in volts.

profile    A cross-section produced from geophysical data.

pseudosection     An image plotting apparent electrical resistivity data against position along a traverse line; this image is produced as an intermediate step to reconstructing the true electrical properties and geometry of a measured transect.


radioisotopic    Relating to natural or human-produced forms of elements that have unstable nuclei and emit radiation during their spontaneous decay to stable forms.

relief    Relative amount of elevation difference of the land surface in a particular area.

resistivity    A measure of how strongly a material or mixture opposes the flow of electric current through it.


saline    At or near the saltiness of seawater.

seismic reflection    A geophysical technique that uses sound waves to detect variations in geologic properties below the Earth’s surface.

shapefile    A data format commonly used for geographic information systems files.

streamer    A cable towed behind a ship that contains electrodes or acoustic sensors.

surface water    Water occurring in the form of a stream, river, lake, estuary, or ocean.


tracer    A natural or artificial element or compound that can be used to detect movement of a fluid, or mixing of one fluid with another.

trackline    An individual segment of a larger marine geophysical survey, often assigned a sequential number that corresponds to the order in which that interval of data was collected.

tributary    A river or estuary that flows into a larger one, rather than discharging directly into a lake or the ocean.


voltage    The driving force that moves an electrical current between two points, measured in units of volts.
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