However, closer examination of the contacts show that these fractures are associated with the cooling process in one very large flow. As the flow cools from the upper and lower boundaries, temperatures may be quite variable. This variability is primarily due to the amount of water passing through the developing fractures resulting in the formation of blocky and irregular structures within the basalt. Pseudo-columns may form also as intermittent, subaerial exposure occurs. Lateral disruption may also occur when an upper solidification front encounters a solidification front rising from below.
Some flows consist entirely of entablature structure.
In Figure 7 Units A and C contain gas vesicles. A continuous supply of a large amount of water filling the fracture systems speeds the cooling process. The cooling is so rapid that the entire flow is cooled from the top down such that the columnar structure does not form near the base. Cooling in a large body of water. Comments Structures within the flows of the Columbia River Basalt Group provide clues to the cooling processes that solidified the lavas.