2. Tectonic activity in the British Isles Learning Outcomes – by the end of this section, you should be able to • show knowledge and understanding of the characteristics and formation of: lava plateau, basaltic columns, volcanic plug; • the causes and impacts of the Dudley earthquake, 2002 (an earthquake in the British Isles) Key Terms
So the edges of plate margins are exciting - and dangerous - places to be. Good job we live no-where near one. Bet you’re happy to be safely tucked up
in your bed at night, safe in the assurance that you’re not going to be engulfed in a surging lava flow, or boiled alive by a pyroclastic flow (remember
Pompeii anyone...?), or rained on by volcanic bombs (car-sized smouldering boulders ejected by volcanic eruptions), or crushed in your bed as your house collapses on top of you during a passing earthquake? There’s a lot to be said for living slap bang in the middle of a plate. Uneventful, bland - and safe!
Fair enough, but wee Northern Ireland didn’t used to be such a quiet and humdrum place to live. Go back
just a few million years into our past, and the landscape would have been radically different. At that time, Ulster would have been subjected to huge volcanic activity that would have literally ripped holes and torn
jagged scars (or fissures) across the earth’s crust. Vast quantities of lava were spewed out over large areas of our Province, radically shaping and changing our landscape.
All of this activity is due to our old friend continental drift. Before the Atlantic Ocean opened up, we lay at
the same plate boundary where Iceland is found today. The forces now at work there were at work here. If you know what to look for, you can see the evidence of this past all our over wee land. We’re going to examine three pieces of such evidence: • • •
lava plateau
basalt columns volcanic plugs
You’re going to do this as an investigative project. See the
Geography website for more details (which will also direct you to a
few BBC video clips outlining Northern Ireland’s volcanic past).
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
2.1 Tectonic features in our own back yard You will be doing a research project on these features. See the additional guiadance sheet and the geography website for more details and instructions.
A. Lava plateau •
Characteristics
•
How it’s formed
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
B. Basaltic columns •
Characteristics
•
How they are formed
C. Volcanic plug •
Characteristics
•
How it’s formed
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
2.2 Earthquakes in the UK Okay, so the UK used to be a much more dangerous place, but good job we don’t need to worry about any of that today. I mean, if we were to have to
worry about earthquakes striking us at any moment, how could we rest easy in our beds tonight? It’s good that all those earthquakes only happen at those
dangerous plate margins, isn’t it? Hold on a minute - you might say to me - why are you not nodding your head in agreement right now? You’re not about to
tell us that earthquakes can strike us today, are you...?!?
Yes, they can! About 95% of the world’s earthquakes occur at plate margins. But the rest can happen pretty much anywhere - including Britain! But before you get too worried, most of them are too small to be noticed by people. It’s only every few years that one will be strong enough to cause some (very, very minor) impacts on humans. Check out the next case study of one such earthquake. You might find that you can rest easy tonight after all…
Dudley Earthquake, 2002 An earthquake in the British Isles
Cause Although the UK no longer lies on a plate margin, we still have many large faults produced when we were last at a plate boundary. Although these faults don’t move as much as those close to plate boundaries today (e.g. the ___________________ in California), still they can shift around a bit from time to time. It was the movement of one of these faults found in the Midlands Microcraton (an enormous 590 million year old band of rock that runs up through Birmingham) that caused the earthquake in Dudley.
Impacts Follow the links on the Geography website to articles that will help you make notes on the impacts of this earthquake. Remember to include facts (i.e. figures and places).
Case studies are a significant part of what it means to study Geography, and they have a significant place in your GCSE exam. To be successful with them in your exam, you must include facts i.e. GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department