Geohazards are defined as hazards lurking below ground. Human interaction may provoke unpredicted disturbance to fine balances in the sub-surface that trigger hazardous conditions, such as mud-slides and eruptions of fluids. In the ocean, the sediments on the seafloor are normally saturated with water, i.e., all the pore-spaces are filled with water. However, it is not as simple as this. On the terrestrial land surface, we all know that there is ground-water filling some of the pore-spaces below ground. Some of our drinking water comes from ground-water sources. In the ocean, the “equivalent” to terrestrial ground-water can be said to be free gas (bubbles). They sometimes occupy the pore spaces of the sediments. In many regions, especially in oil-producing regions, there are large amounts of “shallow gas”, which is considered as being a very dangerous geohazard. In the Caspian Sea and also in the Gulf of Mexico (GoM), there are seafloor mud volcanoes. They feed liquid mud, gas and oil to the seafloor surface, and are sourced from deep reservoirs of over-pressured gas, often in the hydrocarbon generating zones of the sedimentary column (see Judd and Hovland, 2008).
Mud volcanoes and all kinds of seeps, including oil seeps are good examples of Geohazard manifestations, and can be visited on land in Azerbaijan (see examples below).
This picture was taken at the Dashgil mud vocano complex in June, 1995, in Azeerbaijan. The guy in the picture is looking at a bubbling “Salse” seep, where saline water flows to the surface of the mud volcano.
More information on this mud volcano can be found in the article:
University of Tromsø, where there will be a course on Marine Geohazards is at: http://en.uit.no/study-catalogue/show-course?p_document_id=293272
A good photo showing how a mud volcano works. The fluids coming to surface in this mud pot at Dashgil mud volcano, Azerbaijan, are: 1) Liquid mud, 2) water, 3) small amounts of liquid oil, and 4) gas (mainly methane). The knife at the right of this mud pot (also called a “gryphon”), is about 15 cm (the visible part of it). See also the article:
mud volcano pictures at Flickr, at: http://www.flickr.com/photos/seepology/page3/