cap rock

or caprock

noun

, Geology.

1. a mass of anhydrite, gypsum, or limestone immediately above the salt of a salt dome.
2. an impervious stratum overlying an oil- or gas-bearing structure.

cap rock

noun

1. a layer of rock that overlies a salt dome and consists of limestone, gypsum, etc
2. a layer of relatively impervious rock overlying an oil- or gas-bearing rock

Word History and Origins

Origin of cap rock¹

An Americanism dating back to 1865–70

Example Sentences

By 5:30 p.m., our class of five was gathered in the Cap Rock parking lot — one of the lots that stays open at night for stargazers.

From Los Angeles Times

After a reminder to bring water and a rundown of Cap Rock Trail, which is a 0.4-mile loop with a bathroom near the parking lot, Norris led us onto the trail to start planning our shots.

From Los Angeles Times

Hiking a social trail behind Joshua Tree National Park’s famed Cap Rock, I came across a peculiar sight that, if you know what you’re looking for, actually isn’t so unusual at all: a crude cross made of dark stones below a scribble of orange graffiti.

From Los Angeles Times

It makes sense, given how drunk Kaufman and Martin were that night; they probably couldn’t haul the heavy coffin to the backside of Cap Rock, where fans frequently erect those makeshift memorials.

From Los Angeles Times

Spokesperson Jennie Albrinck said National Park Service officials are discussing a music-related exhibit at Cap Rock that would spotlight Native American bird singers, Parsons and emerging artists performing at music festivals such as Coachella and Stagecoach today.

From Los Angeles Times