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The Geological History of the United Kingdom. Natasha Lee University of Edinburgh. The UK’s story really got started about 550 million years ago, in a period of time geologists call the Cambrian
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The Geological History of the United Kingdom Natasha Lee University of Edinburgh
The UK’s story really got started about 550 million years ago, in a period of time geologists call the Cambrian • At this time, Scotland and the rest of the UK were separated from each other by a large ocean called the Iapetus Ocean. • Scotland sat near the Equator and was attached to North America and Greenland. England was attached to Africa, South America etc...and was actually floating around near the South Pole • Russia and Scandinavia were plodding around on their own somewhere in between
Cambrian period – 550 million years ago Iapetus Ocean
In order to understand how the two countries came together, we must first understand a little bit about PLATE TECTONICS • Remember those round boiled sweets that have different layers of colour moving from the centre to the edge? Well the Earth has layering just like that: • Inner core – the middle bit. It’s made of really hot, really squashed solid iron and nickel • Outer core – surrounds the inner core and is made of really hot liquid iron • Mantle – Surrounds the outer core and makes up most of the Earth’s volume. It’s made of solid rock • Crust – the thin surface of the Earth that we live on. • The crust generally not more than 100km thick. That’s quite thin when you think that the Earth is 6370km thick from core to crust (radial thickness)
The mantle is so hot that over millions of years it can flow by the process of convection. This is because the centre of the Earth is very hot, and convection is the best way to cool it down Cold Think of boiling water bubbling in a pan and you’ve got convection currents... just like in the mantle Very hot
The Earth’s crust is divided into a number of segments, that we call tectonic plates. • These plates contain OCEAN CRUST, which is heavy, and CONTINENTAL CRUST, which is light. • Because of convection, all these plates are constantly moving. Where they meet, at PLATE BOUNDARIES, we get volcanoes and earthquakes
Getting back to our story... • 550 million years age, England broke away from Gondwana (i.e. South America, Africa etc...) and started the long journey north
Cambrian period – 550 million years ago Iapetus Ocean
Late Cambrian – 500 million years ago Iapetus Ocean
Getting back to our story... • 550 million years age, England broke away from Gondwana (i.e. South America, Africa etc...) and started the long journey north • It did this by rifting and seafloor spreading. One of those mantle convection currents rose up underneath England and started pushing it away from Gondwana, leaving the Rheic Ocean behind it
Making new crust at ocean ridges ... 4) Where these two PLATES split apart, volcanoes erupt LAVA and make new crust. 3) Ocean crust above the mantle is dragged sideways too Oceanic crust 2) As the mantle cools, it stops rising and moves sideways Upper Mantle 1) Convection brings material up from the deep Earth
Getting back to our story... • 550 million years age, England broke away from Gondwana (i.e. South America, Africa etc...) and started the long journey north • It did this by rifting and seafloor spreading. One of those mantle convection currents rose up underneath England and started pushing it away from Gondwana, leaving the Rheic Ocean behind it • As England moves north, the Iapetus Ocean gets smaller and the Rheic ocean gets larger
Ordovician period – 490-450 million years ago Iapetus Ocean Rheic Ocean
Getting back to our story... • 550 million years age, England broke away from Gondwana (i.e. South America, Africa etc...) and started the long journey north • It did this by rifting and seafloor spreading. One of those mantle convection currents rose up underneath England and started pushing it away from Gondwana, leaving the Rheic Ocean behind it • As England moves north, the Iapetus Ocean gets smaller and the Rheic ocean gets larger • Eventually, the Iapetus Ocean disappears when England collides with Scotland during the Silurian period. Ironically, the geological boundary between England and Scotland is roughly where the modern geographical boundary lies!
This is what happens when 2 bits of continental crust collide... 2 continents are moving together Rheic Ocean Ocean crust is being formed here When the 2 continents collide they stack up and form mountains Convection currents
The Caledonian mountains 450 million years ago? • The collision formed a massive range of mountains called the Caledonides • These mountains may have been as high as the Himalayas • The remains of these mountains are seen today in North America, Norway and ...
After the collision....the Devonian period (420-360 million years ago) • Massive rivers start wearing away the Caledonian mountains, and deposit bits of ground-up rock and sand into huge valleys. • Life on land is just getting started. Plants and trees start growing. We can find plant fossils of this age in Aberdeenshire
Devonian sandstones • The sand deposited from these rivers is turned into sandstone over millions of years. • Sometimes these sandstones preserve fossil sand ripples like the ones you can see on a beach (only without the footprints)
