The extraordinary rock formations that are littered throughout Banks Lake National park and its surrounding cities provide for quite a breathtaking sight. The rock formations on display there are mostly mafic with felsic rocks being sprinkled in here and there. Basalt rocks make up the majority of the national park and were created by series lava flows and millions of years ago, from a Composite Volcano.
Steamboat rock lies at the center of Banks Lake and is by far the most famous rock there. It has a very unique look, the rock appears to have several almost equal layers all the way to the top. This was most likely cause by erosion of a pluton after years of separate but compiled lava flows that hardened; and with help from weather and the Columbian River this puton was exposed. The lava flows that formed Steamboat rock also help explain the existence of numerous solidified horizontals fractures; also know as sills, in other rocks nearby. These sills and other rock formations such as free standing dikes are what helps draw people from all over the world and fuel Banks Lakes tourist based economy, especially in the winter when the lake is frozen over.
