Rocky Hill Ridge, also known as the Mount Lucas-Rocky Hill Ridge, named after Lucas Voorhees, an 18th century landowner, is a diabase

Diabase

Diabase or dolerite is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. In North American usage, the term diabase refers to the fresh rock, whilst elsewhere the term dolerite is used for the fresh rock and diabase refers to altered material...

 trap rock

Trap rock

Trap rock is a form of igneous rock that tends to form polygonal vertical fractures, most typically hexagonal, but also four to eight sided. The fracture pattern forms when magma of suitable chemical composition intrudes as a sill or extrudes as a thick lava flow, and slowly cools.Because of the...

 ridge running west to east in the U.S. State

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of New Jersey

New Jersey

New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...

. Diabase intrusions form Baldpate Mountain and Pennington Mountain, the Mount Rose

Mount Rose (New Jersey)

Mount Rose is a narrow section of the Rocky Hill Ridge in Hopewell Township, New Jersey which is 420 feet above sea level. The ridge's western end is at The Sourlands at Hopewell-Pennington Road and its eastern end is near Province Line Road. The ridge is a diabase intrusion and unlike many of...

 extension of the Mount Lucas-Rocky Hill ridge, and part of the Sourland Mountain

Sourland Mountain

Sourland Mountain is a long ridge in central New Jersey, extending from the Delaware River at Lambertville to the western end of Hillsborough Township near the community of Neshanic , through Montgomery Township and into Hopewell Township in Mercer County. It comprises the largest contiguous...

s. The Ridge is nine miles long and continues across the Millstone River

Millstone River

The Millstone River is a tributary of the Raritan River in central New Jersey in the United States.The Millstone River begins in western Monmouth County and flows northward through southern Somerset County into the Raritan River at Manville. Almost three quarters of its length is paralleled by...

, just below The Georgetown Franklin Turnpike

County Route 518 (New Jersey)

County Route 518 is a county highway in the U.S. state of New Jersey. The highway extends from Route 165 in Lambertville to Lincoln Highway in Franklin Township...

, as the Ten-Mile Run Mountain and Lawrence Brook Mountain. The western section of the ridge, which runs to the northwest to The Sourlands

The Sourlands

The Sourlands is a region in the U.S. state of New Jersey that includes portions of Hunterdon County, Mercer County and Somerset County. It is centered around Sourland Mountain and comprises parts of Lambertville, East Amwell, West Amwell, Hillsborough, Hopewell Boro, Hopewell Township, Montgomery...

 (although not connecting with it because of the Hopewell Fault) is the Mount Rose

Mount Rose (New Jersey)

Mount Rose is a narrow section of the Rocky Hill Ridge in Hopewell Township, New Jersey which is 420 feet above sea level. The ridge's western end is at The Sourlands at Hopewell-Pennington Road and its eastern end is near Province Line Road. The ridge is a diabase intrusion and unlike many of...

section of the ridge.