Geology and Hydrology of the USGS Site
Leesburg Conglomerate
Conglomerates are sedimentary rocks that are made up of various fragments of rock interspersed with finer grained material.
Cordierite Hornfels
Hornfels rocks are metamorphic rocks. They usually start out as sedimentary rocks like sandstone or shale, but then volcanic material pushes up.
Cockeysville Marble
Marble is famous metamorphic rock known for its use in sculpture and architecture.
Diopside Crystals
Diopside crystals are made up of Magnesium, Calcium, Silicon, and Oxygen, and are usually found in metamorphic rocks.
The USGS National Center site straddles the boundary of the eastern edge of the Triassic lowland and the margin of the Piedmont crystalline rock province. The Piedmont upland at the east side of the site is underlain by the Peters Creek Schist, a foliated metamorphic rock that is probably 550 to 650 million years old.