London–Brabant Massif

The massif also occurs in the Belgian subsurface, where it is bounded to the northeast by the Roer Valley Graben that runs diagonally through Dutch Limburg.

The massif is composed of crystalline basement (metamorphic and igneous rocks) with Proterozoic to early Paleozoic ages.

On the island's southern shore, it left the Dinantian, Namurian and Westphalian coal fields of France, Belgium and western Germany.

To its northwest, the thinner crust between it and the Market Weighton Axis was crumpled between the blocks leaving low ridges of wet land between strips of water such as the Widmerpool Gulf.

On the north Norfolk coast, the line of the Carboniferous shore roughly coincides with the modern one.2 As the continent drifted northwards, away from the Equator, through the latitudes represented today by the Sahara desert, the erosion was renewed.

The point in the present context is that the stability of the island contrasts with the relatively unstable crust to its south, which was forced into a long mountain ridge.

This provided the alternating porous and impervious rocks which have trapped the gas escaping when the coal measures, below were subjected to geothermal heat.

This happened because the Pacific Ocean bed swelled up causing the world's seas to rise but also, the process released much carbon dioxide.

It depresses the boundary of the crust and the mantle (Mohorovičić discontinuity, commonly Moho) to depths greater than 40 kilometres as against a figure at the top of the continental shelf of about thirty and less than fifteen below oceanic depths.3 The map shows that there is some tendency for such seismic activity as there is in the region to occur around the margin of the massif.