Trimble Knob facts for kids
Quick facts for kids Trimble Knob |
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![]() Photo of Trimble Knob, taken December 2011
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Highest point | |
Geography | |
Location | Southwest of Monterey, Virginia |
Geology | |
Age of rock | 35.0 ± 0.5 Ma |
Mountain type | Eroded volcano or diatreme |
Last eruption | 35 Ma |
Trimble Knob is a special hill found southwest of Monterey in Highland County, Virginia. It looks like a cone, similar to a pointy hat. This hill is made of a dark, hard rock called basalt. Basalt is a type of volcanic rock, meaning it came from a volcano.
Trimble Knob is actually what's left of an old volcano or a deep volcanic pipe called a diatreme. It last erupted about 35 million years ago. This makes it one of the newest volcanoes on the eastern side of North America.
What is Trimble Knob?
Trimble Knob is a lonely, cone-shaped hill. It stands out in a mostly flat valley surrounded by farms. The top of the hill is 3,123 feet (952 meters) high. U.S. Route 220 runs along the side of the hill. Trimble Knob is the clearest example of many places where melted rock pushed up through the ground in this area.
What is Trimble Knob Made Of?
The middle part of Trimble Knob is made of basalt rock. This basalt area is about 150 meters (164 yards) wide. The basalt pushed its way through older layers of rock. These older rocks are from a time called the Devonian period. They include a type of rock called Needmore Shale, which has fossils in it.
How Old is Trimble Knob?
Scientists first thought the basalt at Trimble Knob was very old, from the Paleozoic Era. They guessed its age by looking at how the rock layers crossed each other.
Later, in 1993, scientists found a more exact age for the basalt. They said it was about 35 million years old. Then, in 2012, other scientists dated the eruption to about 48.86 million years ago. Both of these dates mean the volcano erupted during the Eocene epoch. This was a time period long after the dinosaurs. The basalt pushed through rocks that were formed during the Devonian period.
Another place called Mole Hill in Rockingham County is very similar to Trimble Knob. Scientists think they formed around the same time. There are also other similar rocks near Ugly Mountain in Pendleton County, West Virginia.