Marine Geohazards

Volcano Eruption- Hunga Tonga-Hunga Ha‘apai, Tonga

2022

Submarine Landslide- Resurrection Bay, Alaska

1964

Tsunami Damage- Natori, Japan

2011

Earthquake Damage- Fourth Avenue, Anchorage, Alaska

1964

Deepwater Horizon Oil Spill, Gulf of Mexico

2016

Viscous Lava- Kīlauea, Hawai‘i

2018

Geologic activity in the ocean can cause dangerous or catastrophic events that threaten lives and critical infrastructure both at sea and on land. The USGS studies these geological events beneath the sea floor, known as marine geohazards, to provide decision makers with the information needed to mitigate risks to human communities, infrastructure, and the environment.

What are marine geohazards?

Marine geohazards, or ‘dangers in the deep’ include earthquakes, volcanic eruptions, submarine landslides, and tsunamis, as well as dissociation of gas hydrates—which can cause seafloor collapse—and oil spills or toxic seeps that affect deep sea life or change the physical characteristics of ocean environments.

Identifying Offshore Hazards Near Power Plants — Marine geohazards, or ‘dangers in the deep’ include earthquakes, volcanic eruptions, submarine landslides, and tsunamis, as well as dissociation of gas hydrates—which can cause seafloor collapse—and oil spills or toxic seeps that affect deep sea life or change the physical characteristics of ocean environments. Explore more Marine Geology.

Possible mud volcano — Marine geohazards, or ‘dangers in the deep’ include earthquakes, volcanic eruptions, submarine landslides, and tsunamis, as well as dissociation of gas hydrates—which can cause seafloor collapse—and oil spills or toxic seeps that affect deep sea life or change the physical characteristics of ocean environments. Explore more Marine Geology.

Science to Address Hazards

Earthquakes, Landslides, and Tsunamis

Computer-generated illustration of colored, high-resolution seafloor map clearly shows a fault and where the seafloor is offset. — Seafloor trace of the Queen Charlotte-Fairweather fault (from top left to bottom right) offsets the edge of the Yakobi Sea Valley off southeast Alaska. This 700-mile-long fault has generated large earthquakes in the past. Future shocks—and tsunamis—could threaten coastal communities in the U.S. and Canada.

Underwater earthquakes and landslides can generate tsunamis that cause hazards for coastal communities. USGS scientists study the subduction zone and the recent history of marine hazards and evaluate the future potential and probable impacts of such events on a regional basis. Quantifying these various hazards (e.g., earthquakes, landslides, tsunamis, and volcanoes) using geological and geophysical data, interpretations, and models improves understanding of the underlying processes of marine geohazards to assess the threats they pose. The USGS develops reliable deterministic and probabilistic estimates of the hazards that are used by engineers and policymakers to help reduce risk.

One barrier to measuring seismic risk has been the scarcity of high-resolution maps of the ocean floor. To fill these gaps, USGS scientists conduct high-resolution mapping offshore, especially near urban regions such as Southern California and the Pacific Northwest that are particularly at risk from seismic hazards. Creating three-dimensional views of the seafloor has given scientists remarkable ways to examine how a fault works, or how fluids may follow underground paths and potentially trigger submarine landslides. These landslides threaten offshore structures such as seafloor pipelines, cables, and equipment for oil and gas exploration. They can also trigger tsunamis that endanger coastal communities worldwide.

To discover a fault’s structure, scientists go to sea to collect streams of data that they turn into comprehensive underwater maps. This type of imaging, along with knowing the age of the sediment along faults and measuring other factors such as magnetics and density, can help tell the story of when the fault last ruptured or how fast it is moving. USGS incorporates these data, which have historically been challenging to collect, into earthquake models to estimate their actual hazard risk. Using high-resolution mapping and seismic technology to gather detailed seafloor data can directly impact human life and cities by improving earthquake and tsunami forecasts.

Research results are used in evaluations of earthquake risk zoning, public disaster education and preparedness, and engineering and building codes. Additionally, reassessing the threat of earthquake, tsunami, and landslide hazards to ports and nuclear power plants can directly impact facility management, emergency-management planning, and plant re-licensing.

The Atlantic and Gulf of Mexico margins are heavily urbanized, support extensive port and industrial/resource facilities, and host 10 nuclear power plants. The USGS completed quantitative assessments of submarine landslides for the U.S. Atlantic coast from Maine to Florida and throughout the Gulf of Mexico to better comprehend the risk of potential submarine landslides and tsunamis to these areas and associated infrastructure.

U.S. east coast preliminary interpretations of large submarine landslides — Preliminary interpretation of large submarine landslide complexes, major submarine fans, and contourite drifts along the U.S. east coast. Explore the Atlantic and Gulf of Mexico Submarine Landslides-Tsunami Hazards Project.

Map of the North American - Caribbean tectonic plate boundary — Puerto Rico and the Virgin Islands are located at an active plate boundary between the North American plate and the northeast corner of the Caribbean plate. Plate movements have caused large magnitude earthquakes and devastating tsunamis. The USGS has an ongoing program to identify and map the faults in this region using various geophysical and geological methods in order to estimate the location and magnitude of potential earthquakes. Explore Caribbean Tsunami and Earthquake Hazards Studies.

Schematic showing the general setting of seeps on the US Atlantic margin and related processes, such as gas hydrate degradation, groundwater seepage, leakage through fractured rocks, or emissions from the seafloor overlying salt diapirs. Learn about Atlantic Margin Methane Seeps.

Gas Hydrates and Seafloor Collapse

Ice-like gas hydrates under capping rock encrusted with mussels on the sea floor — Ice-like gas hydrates under capping rock encrusted with mussels on the seafloor of the northern Gulf of Mexico.

Naturally occurring gas hydrates are ice-like combinations of water and (usually methane) gas that form in sediment below the sea floor and in areas of continuous permafrost when pressure and temperature conditions are appropriate.

In deep water marine settings where warm fluids are pumped from great depths below the seafloor for extraction of conventional oil and gas, heating of sediments near a well could lead to breakdown of gas hydrates and release gas and water. Intact gas hydrates generally strengthen marine sediments, and dissociation of gas hydrates could lead to subsidence or collapse of the seafloor near the well. Features associated with natural failure of the seafloor (landslides) have also been linked to gas hydrates in some cases. USGS scientists support submarine geohazards research through field-based surveys that refine understanding of the hydrates-slope failure association and through geotechnical studies that evaluate the response of sediments to dissociation or dissolution of gas hydrates.