Figure 6. Seismic reflection profile from the Belfast Bay pockmark field (modified from Kelley and others, 1994). The seismic profiler sends sound energy into the seafloor where it reflects back from layers of sand and mud over the bedrock. Glacial-marine material is well layered and occurs on land as eroding bluffs visible along the coast. Its upper surface is a dark reflector formed as the bluffs erode, and is covered by Holocene mud. Natural gas obscures the acoustic signal, but is absent where gas has escaped and a pockmark is seen.
Last updated on October 6, 2005