Cobb–Eickelberg Seamount chain

The Cobb-Eickelberg seamount chain is a range of undersea mountains formed by volcanic activity of the Cobb hotspot located in the Pacific Ocean.

Axial is the youngest seamount and is located approximately 480 km west of Cannon Beach, Oregon.

Given the length of the chain this hotspot must have been active over a period of at least 30 million years (probably longer since older seamount would have been subsided).

It went under the Juan de Fuca Ridge when the Pacific plate started moving northwest and eventually the boundary came right on top of the hotspot.

[3] 42% of the lava surrounding the volcano ranges from ropy, whorly, or lineated pāhoehoe to jumbled chaotic form.

[4] Colonial protozoans, bacterial mats, pogonophorans, metazoans, polychaetes, bivalves, tubeworms, copepods and many other organisms are found in the region where there are hydrothermal vents present in the caldera.

Due to its separation from the Juan de Fuca ridge, spreading has very little effect on Brown Bear, so it is not as geologically complex and is not studied in detail.

[5] Geographically, the Brown Bear Seamount is separated into two areas, Northwestern and Southeastern, with distinct morphological features.

The morphology of the western portion also suggests that it was formed before the hotspot interacted with the Juan de Fuca ridge.

[6] The northwestern section of Brown Bear is dominated by a large (5 km diameter) rounded volcanic cone structure.

[6] The southern portion extends south of 46.1 degrees North Latitude, and consists of relatively small (1–2 km diameter) volcanic cones.

The Cobb Seamount is all basalt and contains phenocrysts of plagioclase and clinopyroxene; the intergranular/interstitial matrix was found to have iron and titanium oxides.

[8] Video and photographs collected in 2012 from Cobb Seamount have shown a wide variety of biodiversity at the location.

[12] The shallow water community mostly consisted of rockfish, flatfish, sea stars and attached suspension feeders.