Cobb Segment

No photo available for this volcano
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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 46.88°N
  • 129.33°W

  • -2100 m
    -6888 ft

  • 331011
  • Latitude
  • Longitude

  • Summit

  • Volcano

The Global Volcanism Program has no activity reports for Cobb Segment.

The Global Volcanism Program has no Weekly Reports available for Cobb Segment.

The Global Volcanism Program has no Bulletin Reports available for Cobb Segment.

Basic Data

Volcano Number

Last Known Eruption



1180 BCE

-2100 m / -6888 ft


Volcano Types

Fissure vent(s)

Rock Types

Basalt / Picro-Basalt

Tectonic Setting

Rift zone
Oceanic crust (< 15 km)


Within 5 km
Within 10 km
Within 30 km
Within 100 km

Geological Summary

The Cobb Segment in the northern part of the Juan de Fuca Ridge, lies south of the Endeavour Ridge segment. Also known as the Northern Symmetrical or NSymm Segment, the 150-km-long Cobb Segment is the longest of the Juan de Fuca Ridge. It has a narrow, 1-2 km wide axial crest with a shallow graben that has a high point at a depth of about 2300 m. A prominent seamount with hydrothermal deposits at its summit lies just west of the axis high and was the source of a broad area of young, mostly sediment-free lava flows. As with other Juan de Fuca Ridge segments, a shallow magma chamber is thought to underlie the Cobb Segment, and a preliminary uranium-series date of Holocene age was obtained on a basaltic lava flow from the Cobb Segment.


The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography.

Carbotte S M, Detrick R S, Harding A, Canales J P, Babcock J, Kent G, Van Ark E, Nedimovic M, Diebold J, 2006. Rift topography linked to magmatism at the intermediate spreading Juan de Fuca Ridge. Geology, 34: 299-212.

Christeson G L, Purdy G M, Rohr K M M, 1993. Structure of the Northern Symmetrical Segment of the Juan de Fuca Ridge. Mar Geophys Res, 15: 219-240.

Goldstein S J, Murrell M T, Janecky D R, Delaney J R, Clague D A, 1992. Geochronology and petrogenesis of MORB from the Juan de Fuca and Gorda ridges by 238U-230Th disequilibrium. Earth Planet Sci Lett, 109: 255-272.

Volpe A M, Goldstein S J, 1993. 236Ra-230Th disequilibrium in axial and off-axis mid-oecan ridge basalts. Geochim Cosmochim Acta, 57: 1233-1241.

Eruptive History

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1180 BCE (?) Unknown Confirmed 1 Uranium-series

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.


NSymm Segment | Northern Symmetrical Segment

The Global Volcanism Program has no photographs available for Cobb Segment.

Smithsonian Sample Collections Database

There are no samples for Cobb Segment in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

Affiliated Sites

Large Eruptions of Cobb Segment Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
MODVOLC - HIGP MODIS Thermal Alert System Using infrared satellite Moderate Resolution Imaging Spectroradiometer (MODIS) data, scientists at the Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, developed an automated system called MODVOLC to map thermal hot-spots in near real time. For each MODIS image, the algorithm automatically scans each 1 km pixel within it to check for high-temperature hot-spots. When one is found the date, time, location, and intensity are recorded. MODIS looks at every square km of the Earth every 48 hours, once during the day and once during the night, and the presence of two MODIS sensors in space allows at least four hot-spot observations every two days. Each day updated global maps are compiled to display the locations of all hot spots detected in the previous 24 hours. There is a drop-down list with volcano names which allow users to 'zoom-in' and examine the distribution of hot-spots at a variety of spatial scales.
MIROVA Middle InfraRed Observation of Volcanic Activity (MIROVA) is a near real time volcanic hot-spot detection system based on the analysis of MODIS (Moderate Resolution Imaging Spectroradiometer) data. In particular, MIROVA uses the Middle InfraRed Radiation (MIR), measured over target volcanoes, in order to detect, locate and measure the heat radiation sourced from volcanic activity.