摘要:

Anyone who spends much time above the treeline has probably seen rock glaciers and paused to wonder about them. Their curious and occasionally spectacular forms (Figure 1) occur in alpine and polar regions throughout the world, yet much remains uncertain about how they develop. A core of ice recently recovered from a rock glacier in the Absaroka Mountains of northwestern Wyoming vividly illustrates several important aspects about rock glaciers. At least some rock glaciers are a form of debris‐covered glacier, and original isotopic stratigraphy may be preserved within their ice. Perhaps most interesting of all, the core of some rock glaciers is composed of layered ice that can be drilled and recovered, and some of this ice is exceptionally ol

ISSN:0002-8606    

DOI:10.1029/96EO00149

年代:1996

数据来源: WILEY

摘要:

A century before the federal government established a council for “sustainable development,” John Wesley Powell was touting the idea as way to tame the American West. Powell's quiver of intellectual tools included one that modern environmentalists swear by: integrated assessm

ISSN:0002-8606    

DOI:10.1029/EO077i023p00218-02

年代:1996

数据来源: WILEY

摘要:

Gas hydrate is a solid phase of water and low‐molecular‐weight gases, mostly methane, that forms in marine sediments when gas concentrations are adequate, temperature is low, and pressure is high. Although gas hydrate may be a common phase in the shallow geobiosphere, little is known about it because it is unstable under normal surface conditions.Leg 164 of the Ocean Drilling Program (ODP) studied natural gas hydrate in marine sediment at the Blake Ridge on the continental margin off southeastern North America and found that it occupies more than 1% of the sedimentary section from 200 to 450 m below seafloor (mbsf). At the Blake Ridge, free gas is dispersed throughout a region a few hundred meters thick beneath the gas hydrate—bearing zone. Coupled with geophysical data indicating that gas hydrate occurs throughout a laterally extensive portion of the Blake Ridge, the drilling confirmed that these sediments contain enormous amounts of me

ISSN:0002-8606    

DOI:10.1029/96EO00152

年代:1996

数据来源: WILEY