caprock

English

Alternative forms

• cap rock

Etymology

cap +‎ rock

Noun

caprock (countable and uncountable; plural caprocks)

1. (geology) A harder or more resistant rock type overlying a weaker or less resistant rock type.
   • 2009 September 3, James Glanz, “Energy Company Calls Halt to Drilling Project”, New York Times:

     Last month, federal scientists said that the company had fallen far behind schedule because a huge rig hired to drill down about 12,000 feet, or more than two miles, on federal land had not been able to pierce surface formations called caprock.