Emperor Seamounts

Emperor Seamounts
Name	Emperor Seamounts
Location	North Pacific Ocean
Coordinates	50°N 170°W
Type	Seamount chain
Age	Eocene–Miocene
Volcanic arc	Hawaiian–Emperor seamount chain

Emperor Seamounts are a submerged chain of extinct seamounts and guyots in the northern Pacific Ocean, forming the northwest extension of the Hawaiian–Emperor seamount chain. The chain links deep oceanic crust structures with paleogeographic records from the Eocene epoch to the Miocene epoch, and provides constraints on the motion of the Pacific Plate, the dynamics of the Hawaiian hotspot, and the palaeoceanography of the North Pacific Gyre.

Geology and Formation

The Emperor chain consists of volcanic edifices built on oceanic plateaus and basaltic substrates erupted by the Hawaiian hotspot and related mantle upwelling. Petrological studies compare tholeiitic basalt samples with alkali basalt suites recovered during expeditions by the Ocean Drilling Program and the Deep Sea Drilling Project, tying geochemical signatures to processes in the upper mantle and mantle plume dynamics. Radiometric dates using argon–argon dating and uranium–lead dating on phenocrysts link emplacement ages to the Eocene and Oligocene, informing models of hotspot-related intraplate volcanism and seamount subsidence driven by isostasy and thermal contraction of the lithosphere.

Geography and Extent

The chain extends northwest of the Hawaiian Islands toward the Aleutian Trench region, stretching across the Emperor Seamounts’ approximate latitudinal band from near the Aleutian Islands to south of the Bering Sea. Major named features include guyots and cones that align along a trend intersecting magnetic anomalies mapped by marine geophysics surveys conducted from RV Melville and USCGC Polar Sea cruises. Bathymetric mapping by the National Oceanic and Atmospheric Administration and the Geological Survey of Japan shows seamount summits, flat-top guyot platforms, and flank terraces that rise above abyssal plains adjacent to the North Pacific Basin and continental margins near Kamchatka and the Aleutian arc.

Volcanic Activity and Age Progression

Age progression along the chain records a change from older northwestern edifices toward younger southeastern features, consistent with motion relative to a mantle source. Work by teams from the United States Geological Survey and the University of Hawaii used paleomagnetism and radiometric chronologies to document an abrupt bend between the Emperor trend and the Hawaiian trend around the transition from the Eocene to the Oligocene. This bend correlates with shifts in plate-motion reconstructions developed by researchers at the Scripps Institution of Oceanography and the Woods Hole Oceanographic Institution. Volcanic activity ceased on Emperor edifices earlier than on the main Hawaiian chain, leaving stratigraphic records of reef development, carbonate capping, and erosional planation preserved in cores analyzed at the Smithsonian Institution and the British Geological Survey.

Tectonic Implications and Pacific Plate Motion

The spatial geometry and timing of Emperor edifices underpin reconstructions of Pacific plate kinematics that involve data from the International Seismological Centre and the Global Positioning System networks. Interpretations include a long-term change in the direction of the Pacific Plate and hypotheses about hotspot drift versus plate reorientation debated among groups at Caltech, Massachusetts Institute of Technology, and the University of Cambridge. Integration of seafloor spreading magnetic anomaly charts, fracture zone orientations cataloged by the National Aeronautics and Space Administration, and mantle tomography images from the European Geosciences Union community support models invoking plume–lithosphere interaction, slab pull forces at the Aleutian Trench, and mantle flow linked to the Cenozoic reorganization of plate boundaries.

Marine Ecology and Sedimentology

Submerged tops of Emperor edifices host benthic communities with biotic assemblages studied by expeditions from the Monterey Bay Aquarium Research Institute and the Japan Agency for Marine-Earth Science and Technology. Cold-water corals, sponge fields, and chemosynthetic faunas occur on high-relief slopes, while sediment drifts capture microfossil assemblages used by paleoceanographers at the Lamont–Doherty Earth Observatory and the Woods Hole Oceanographic Institution to reconstruct past North Pacific Current variability. Sediment cores recovered by the Chikyū and research vessels exhibit pelagic ash layers correlated to eruptive events cataloged in the Global Volcanism Program and to changes in planktonic foraminifera assemblages studied by the Paleontological Society.

Discovery and Research History

First charted on early 20th-century hydrographic charts compiled by the United States Navy and later mapped in detail during Cold War-era surveys by the Scripps Institution of Oceanography and Lamont Geological Observatory, the chain entered scientific literature through descriptions by researchers affiliated with the Geological Society of America and the American Geophysical Union. Key breakthroughs arose from drill cores obtained under the International Ocean Discovery Program and from geophysical data collected during joint expeditions involving the Canadian Institute of Ocean Sciences, the National Oceanography Centre (UK), and institutions in Japan and Russia. Contemporary research continues under collaborative programs funded by agencies such as the National Science Foundation and coordinated through consortia including the International Continental Scientific Drilling Program and regional working groups of the Intergovernmental Oceanographic Commission.

Category:Seamounts of the Pacific Ocean