Redwood National and State Parks: Ancient Forests on Restless Ground

The ancient redwood groves of northwestern California stand on some of the most restless ground in the country. The North Coast region is one of the most seismically active in the United States, with frequent earthquakes and rapid uplift that trigger landslides, shift rivers and wear the coast away fast. The rock beneath the forest was itself scraped off the ocean floor.

Redwood Creek. Image from the National Park Service's Geologic Resources Inventory.

The parks

Redwood National and State Parks lie in the western Klamath Mountains, about 18 km (11 miles) south of the California–Oregon border in Del Norte and Humboldt Counties. Established on October 2, 1968, they protect about 56,251 hectares (138,999 acres) of prairies, oak woodlands, wild rivers, coastal redwood forest with virgin groves of ancient trees, and nearly 56 km (35 miles) of rugged Pacific coastline. Rich in biodiversity, the parks were designated a World Heritage Site on September 2, 1980.

Rock from the sea floor

Most of the parks' bedrock is the Jurassic–Cretaceous Franciscan Complex, an accretionary assemblage: rock added to the edge of the continent by plate tectonics, sheared and uplifted from the ocean floor. Younger units lie on top of it:

Rivers and a fault

Three large river systems — the Smith River, the Klamath River and Redwood Creek — have cut down through the bedrock to carve deep gorges through the forest and mountains. In the southern part of the parks, Redwood Creek runs northwest along the trace of the Grogan Fault, in a long, narrow basin fed by many small, steep tributaries.

The mouth of the Klamath River. Image from the National Park Service's Geologic Resources Inventory.

The parks belong to the Pacific Border physiographic province and share its geologic history, and some of its characteristic formations, with a region far beyond their boundaries.

Maps and inventories

The Park Service's Geologic Resources Inventory, which produces digital geologic maps and reports for more than 270 natural resource parks, has mapped the geology of the parks' northern and southern portions, and a Soil Resources Inventory has been completed. Both are on the NPS DataStore.

Sources

Based on "NPS Geodiversity Atlas—Redwood National and State Parks, California," National Park Service Geologic Resources Inventory, which cites Anderson (2017) and Bero et al. (2020); a work of the United States government in the public domain.