London–Brabant Massif

The London–Brabant Massif or London–Brabant Platform is an important part of Europe's structure. It stretches from the Rhineland in western Germany across northern Belgium and the North Sea to places like East Anglia and the middle Thames in southern England. This area is like a high, stable block of land in the Earth's crust.

In Belgium, the massif continues underground, bordered by the Roer Valley Graben that runs through Dutch Limburg. Sometimes, the Midlands Microcraton in southeastern Wales and western England is also included, leading to names like Wales–Brabant Massif or Wales–London–Brabant Massif.

This massif was once part of a small continent called Avalonia. Over time, it has bordered different geological areas, such as the Rhenohercynian Zone to the south. In the past, during certain times in Earth's history, the London–Brabant Massif was an island known as the London–Brabant Island.

Formation

The London–Brabant Massif is made from strong, old rocks formed long ago. These rocks are mostly from a time when Earth was very young, between the Proterozoic and early Paleozoic periods. They were changed and shaped by big movements in Earth's crust during two major events called the Cadomian and Caledonian orogenies, which happened hundreds of millions of years ago.

This strong base of rocks is usually covered by layers of younger rocks, except in some parts of southwest England and Wales. The land piece called Avalonia used to be part of a large ancient continent named Gondwana. Over time, Avalonia moved to lower areas of the Earth, passing through dry places similar to the Namib Desert today. This movement caused the older rock layers to become complex and hard to study because they are deep underground.

Carboniferous period

The Carboniferous period was an important time for Europe. As the land moved near the Equator, thick tropical forests and swamps grew on its shores. These forests and swamps created rich coal fields in places like France, Belgium, and western Germany.

To the northwest, the land between this area and the Market Weighton Axis was pushed and folded, creating low, wet areas with strips of water. Here, coal formed in places like Leicestershire, Nottinghamshire, and Derbyshire. These coal layers stretch far east but are now deep underground. On the coast of modern Yorkshire and Lincolnshire, the top of these old coal layers is about 2 kilometers below the surface. The Carboniferous shoreline on the north coast of Norfolk is close to where it is today.²

The Permian and Triassic

As the land moved north away from the Equator, erosion began again. This created soils similar to those found in the Sahara desert, now seen in places like the New Red Sandstone and the red soils of Leicestershire and Rutland.

During the early Permian, big shifts in the Earth's surface happened as lands to the south pressed against an island. These changes can be seen in areas like Brittany, the Ardennes, and the Rhineland. In southern England, these shifts are hidden under layers of chalk from a later time called the Upper Cretaceous. Meanwhile, to the north, important changes were happening. Western Britain rose up, while eastern Britain, including the island, sank down. This created a shallow sea in a dry climate. Over time, this area filled with desert sands, salts, and mud, forming layers of rock that later trapped gas from deeper layers heated by the Earth. This led to the discovery of gas fields off the coast of Norfolk.

Rhaetic transgression

In the early Jurassic, the Rhaetic sea covered much of the Permian plain. Near the edge of the London–Brabant Island, areas with river-like conditions created the Lower Estuarine Series for some time. Then the sea rose and formed the Lincolnshire limestones, before dropping again to leave the Upper Estuarine Series. The sea rose once more to form the Blisworth Limestone, the Blisworth Clay, and the Upper Jurassic clays.

A similar pattern happened in France, causing the Paris Basin to flood from Anjou to Luxembourg.

Cretaceous

During the Cretaceous period, the land sank lower compared to the sea level. Near the end of this time, the British part became covered by chalk from the Upper Cretaceous. This happened because the floor of the Pacific Ocean rose, making sea levels go up. It also let out a lot of carbon dioxide.

Modern existence

We can think of this area as a thick piece of Earth's crust that sits deep below the surface, covered by thinner rocks. This thick block pushes the boundary between the crust and the softer layer below it, called the mantle, down to depths more than 40 kilometres. In places where there is less thick crust, like on the edges of continents, this boundary is much shallower.

Maps show that any shaking from earthquakes in this area usually happens near the edges of this thick block of crust. Two notable examples are the Dover Straits earthquake of 1580 and the 2008 Lincolnshire earthquake.