cap rock
Americannoun
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a mass of anhydrite, gypsum, or limestone immediately above the salt of a salt dome.
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an impervious stratum overlying an oil- or gas-bearing structure.
noun
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a layer of rock that overlies a salt dome and consists of limestone, gypsum, etc
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a layer of relatively impervious rock overlying an oil- or gas-bearing rock
Etymology
Origin of cap rock
An Americanism dating back to 1865–70
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
An almost kilometre thick layer of clay or cap rock will lock away the CO2, just as it trapped oil and gas for millions of years, Schovsbo explains.
From BBC ● Jan. 29, 2026
At a CCS plant, the carbon gas will be compressed into a liquid form, pumped downward into porous rock underneath a layer of impermeable rock, known as cap rock.
From BusinessWeek ● Feb. 7, 2012
Lubbock, dry and bleak, is 318 miles from Dallas on the flat cap rock of west Texas.
From Time Magazine Archive
I could soon talk glibly of "blossom rock," "pay streaks," "cap rock," "wall rock," "rich color," and use the common terms of miners.
From A Gold Hunter's Experience by Chalkley J. Hambleton
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
