An anticline is a type of geological fold that forms when rock layers are compressed and arch upward. This structure resembles an upside-down U shape, with the oldest rock layers located at the core of the fold. Anticlines are important in geology because they can trap oil and natural gas, making them significant for energy exploration. These formations are often found in areas where tectonic plates collide, leading to the bending and folding of the Earth's crust. Understanding anticlines helps geologists study the history of the Earth's surface and locate resources like petroleum and natural gas.