Mathews based this on the age of the underlying till, the existence of pillow lava close to the bottom of some lavas, indicating subaqueous volcanism, the columnar jointing at the edges of the lavas, indicating rapid cooling, and the absence of apparent palaeogeography.
Under these conditions, masses of rock measured in thousands of cubic kilometres are torn loose by gravity and fall and/or slide, often moving hundreds of kilometres in a "geologic instant" to a lower resting place (in some cases lubricated by subaqueous avenues).
Such subaqueous currents occur because some of the water in an ocean or lake is colder or saltier or contains more suspended sediment and, thus, is denser than the surrounding waters.
Recent field based observations confirm the presence of widespread phreatomagmatic pyroclastic rocks; however, some that had been interpreted as being subaqueous exhibit textural features that are more consistent with subaerial depositional environments.
We note, however, that at least some of these ashes may also be subaqueous in origin.
Thus, depending on the timing of the lake disappearance in relation to the landslide events, it is possible that at least some of the most ancient landslides were subaqueous.
Low river flows from 2007 to 2010 due to an unprecedented drought, resulted in 71 wetlands along 210 km of the River Murray below Lock 1 in South Australia becoming dry, exposing the normally subaqueous soils in wetlands and, in some instances, causing severe soil acidification.
Coarse angular sands probably were deposited from turbidity currents (subaqueous sediment-laden flows); the extraordinary coarse conglomeratic mudstones in some flysch may be a product of submarine mudflows.
An attempt to recapture some of that enchantment — a word not much used in conjunction with subaqueous motoring these days — is on display through July 1 in Hoboken, the dense city bracketed north and south by two unseen and mostly unloved feats of civil engineering: the Lincoln and Holland tunnels, through which 76 million vehicles travel each year, few of them honking for joy.
The sheer depth of some footprints, they added, suggested that the creatures crawled on dry land "because subaqueous organisms are buoyed up as they walk".
