Geology of Redwood National Park
Redwood National Park and the three state parks that adjoin it protect the heart of the remaining coast-redwood forest, a 500-mile swath of the tallest trees anywhere in the world. While the redwoods themselves are mighty, their geologic context is equally dramatic: a story of the earth's restless upheaval.
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North Coast Ranges
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Like the rumpled highlands north along Oregon's Pacific margin, the primary cause of California's North Coast Ranges' formation was marine sediments' slough onto the North American continent as oceanic plates subducted, or slid beneath. The oldest of these rocks in the Redwood National Park area -- transformed mud and sands -- appear to have been piled off the subduction zone some 100 million years ago.
Rock Types
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A variety of sedimentary rock types comprise these North Coast Ranges. In "A Sierra Club Naturalist's Guide to the Pacific Northwest" (1989), Stephen Whitney lists sandstones, shales, cherts and limestones chief among them, with some exposures of serpentine and basalt.
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Other Geologic Forces
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The same active tectonic forces that built up the Coast Ranges also cause earthquakes in redwood country. Offshore subduction, according to Harris et al's "Geology of National Parks" (2003), may be causing this section of California to slope seaward, forming Redwood National Park's coastal lagoons. Other geologic forces include stream deposition and erosion, landslides and the occasional tsunami generated by oceanic earthquakes.
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References
Resources
- Photo Credit redwood sun image by Dennis Carrigan from Fotolia.com
