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A GLOBAL OUTLOOK ON METHANE GAS HYDRATES
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The Deep Sea Drilling Project (DSDP) (1968-1983, Legs 1-96)
introduced R/V Glomar Challenger, the first international
drilling platform for global studies of gas hydrates in the
marine environment (Figure TB1.1). Over the course of several
DSDP legs, scientists obtained the first tangible proof that gas
hydrates exist in a variety of geologic settings, evidence that
gas hydrates could be nearly ubiquitous in continental-margin
and slope sediment around the world.
An objective of DSDP Leg 11 in 1970 was to investigate the
nature of the anomalous acoustic reflections (called Bottom
Simulating Reflectors or BSRs) that parallel the sea floor.
They had been observed on seismic profiles of the passive
margin along the Blake Outer Ridge in the Atlantic Ocean.
The expedition recovered sediment cores with methane
concentrations so high that, in many cases, gas expansion
was sufficient to extrude sediment from core liners. Although
no obvious gas hydrates were recovered on Leg 11, the high
gas concentrations and presence of the BSR were suggestive
enough for the R/V Glomar Challenger to return in 1980
(DSDP Leg 76) with an objective of recovering gas hydrates.
This objective was met with the recovery and testing of a gas
hydrate specimen with a high concentration of methane.
A year earlier, in 1979, gas hydrates were recovered in the
active margin setting along the landward wall of the Middle
America Trench during DSDP Leg 66 off Mexico and Leg 67 off
Guatemala. The primary gas from hydrate specimens at both
sites was methane, which was confirmed by a massive gas-
hydrate specimen recovered in 1983 during Leg 84 near the Leg
66 sites. Although a BSR was present at the Leg 66 hydrate-
Box 1.1
Gas Hydrate and the Deep Sea Drilling Project
recovery sites, the Leg 67 hydrate recoveries were in vitric, or
glass-like, sands with no associated BSR.
Yet another hydrate-bearing geologic setting was discovered
in 1983, when DSDP Leg 96 recovered gas-hydrate nodules
and crystals in Gulf of Mexico mud. Taken together, these
sites provided a particularly significant result of the Deep Sea
Drilling Project by showing how gas hydrates were present
in sediments from a wide range of geologic environments.
Extrapolation of these results suggests that gas hydrates
are ubiquitous in continental-margin and slope sediment
around the world, and this assumption has been confirmed by
subsequent investigations.
marine discoveries made in the early 1980s during scientific
expeditions by the Deep Sea Drilling Program’s R/V Glomar
Challenger (see Text Box 1.1), however, that gas hydrates were
recognized as a significant part of the natural environment. It
was soon realized that such a large, and previously unappre-
ciated, storehouse of organic carbon and its inherent energy
potential could have profound implications for society and our
understanding of Earth (Kvenvolden 1988a, b; 2000).
Figure TB-1.1:
The R/V Glomar Challenger (Courtesy of the U.S.
Geological Survey).