Types of Rock
At Redwood National Park, you will find sedimentary, metamorphic and transitional rocks. Sedimentary rocks, consisting of sandstone, mudstone and pebble conglomerates, serve as ground water reservoirs for the redwood forests. When the sedimentary rocks become hot enough, they create metamorphic rocks. Transitional rocks are stuck between the sedimentary and metamorphic states. You can find examples of sedimentary rocks at the Gold Bluff Formation, which was named for the small gold flakes pioneers found in the bluffs' black sands.
Seismic Activity
Earthquakes are very common in California, and Redwood National Park seems to know them the best. The area is prone to more seismic activity than anywhere else in the United States. The North American, Pacific and Gorda tectonic plates meet right off the shore at Cape Medocino, 100 miles southwest of the park. Although most of the earthquakes caused by the friction between these plates are small, nine earthquakes reaching above a 6.0 on the Richter Scale rattled the coast during the 1990s and an 8.0-plus magnitude earthquake is possible in the future. Most of the earthquakes occur offshore, which causes tsunamis to form.
Formations
Visitors can see the influence the ocean has had on the California coastline. The wind and waves carry sand and move it, which creates sand dunes. The Klamath River and longshore drift, the southward movement of coastal sediment, cause submerged sandy ridges called spits. The rocky crags that peek out from the ocean's blanket of water were once sea cliffs that have now succumbed to the movement of the tectonic plates.