Franciscan Abstract
Digital Infrared, Ortho Kite Aerial Photography
Eroding Franciscan Formation on the headland between Big Lagoon and Dry Lagoon, Humboldt County, California. The bedrock is a melange -- a chaotic mudstone studded with giant resistant boulders (technically "knockers") of metavolcanic and metasedimentary rock. This complex was created at the boundary of the Juan de Fuca and North American plates as the former was subducted. Marine shales, sandstones, cherts, and basalts were scraped off on the overlying plate. Metamorphic rocks may have been uplifted from deep in earth by buoyant serpentine in the boundary zone. Further south some knockers are blueschist grade, coming from 15 to 30 km depth.
These rapidly eroding headlands supply sand which isolates several large lagoons along the Humboldt County coast.
Franciscan Abstract
Digital Infrared, Ortho Kite Aerial Photography
Eroding Franciscan Formation on the headland between Big Lagoon and Dry Lagoon, Humboldt County, California. The bedrock is a melange -- a chaotic mudstone studded with giant resistant boulders (technically "knockers") of metavolcanic and metasedimentary rock. This complex was created at the boundary of the Juan de Fuca and North American plates as the former was subducted. Marine shales, sandstones, cherts, and basalts were scraped off on the overlying plate. Metamorphic rocks may have been uplifted from deep in earth by buoyant serpentine in the boundary zone. Further south some knockers are blueschist grade, coming from 15 to 30 km depth.
These rapidly eroding headlands supply sand which isolates several large lagoons along the Humboldt County coast.