Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The large La Reforma Caldera is located on the eastern coast of the central Baja California Peninsula, facing the Gulf of California, near Santa Rosalia, Baja California Sur. The outer rim of the caldera is defined by dark-colored rocks made out of very fluid lava. A dome of rock in the center of the caldera is a resurgent dome. A resurgent dome is formed as the floor of the caldera is heaved upward by the movement of magma below ground. The lavas surrounding the caldera date to about 1 million years ago.