Download Plate tectonics Tectonic activity – movements within the Earth cause

PLATE TECTONICS
Tectonic activity – movements within the Earth cause earthquakes and volcanoes, the time cannot be predicted but
scientist can identify which parts are most likely to be affected
Earthquakes – there is defined distribution pattern of earthquakes which occur in long narrow belts
Volcanoes - there is defined distribution pattern of volcanoes located in long narrow belts – zones of activity
Plates – the Earth’s crust is broken into several segments which float on the mantle, convection currents cause
them to move – few centimetres a year, there are two types – continental (old and permanent) and oceanic (younger
and constantly changing)
Plate boundaries – where the plates meet, most earthquakes and volcanoes occur there, little activity takes place
in the centre of plates
Constructive – two plates move away from each other, magma rises and forms new oceanic crust, the Atlantic
Ocean is widening by 3 cm a year, new islands can come into being
Destructive – oceanic crust moves towards plates of continental crust, oceanic crust moves downwards, it melts
(heat and friction), severe earthquakes, magma can rise to the surface and form volcanoes and long chain of islands
Collision – two continental plates move together, because it cannot sink, rocks are forced upwards to form fold
mountains
Conservative – two plates slide past one another, no crust created or destroyed, no new landforms, plates tend to
stick and after pressure is built up, shockwaves cause earthquakes
Eruptions – take place where the magma rises to the surface, increasing of pressure, usually accompanied by
earthquakes, a crater created, eruptions of steam and ash, most time inactive, landslide of rock, glacier ice and soil,
mudflow, blast waves of volcanic gas, steam and dust, volcanic bombs, thicker ash drifted away, fine ash moves
around the Earth, deaths caused by poisonous gasses, settlements destroyed, death of fish in lakes and rivers due to
ash, roads and railway bridges washed by floodwaters, living organisms and forest destroyed, electricity supplies
interrupted and telephone wires cut, crop lost by setting dust, livestock closest to the eruption killed, material
effected from the volcano rapidly break down into fertile soil, evacuation, resettlement, monitoring,
Prediction - eruptions are easier to predict than earthquakes – tremor, ground temperatures rise, swelling of the
volcano, before eruption gas and steam emitted,
Preparation – setting up monitoring, preparing evacuation plan, training emergency services, organising
emergency services, post eruption plans
Earthquakes – measured in Richter scale, each level 10 times stronger, buildings, bridges, highways and rails
collapse, supplies disrupted, fires caused by broken gas pipes, gridlock of roads delaying ambulances and fireengines, homeless, shortage of basic staff, aftershocks, deaths, closure of factories, water rises to ground level and
causes building to collapse (clay),
Prediction – harder to predict the time than location, install sensitive instruments, map frequencies of previous
earthquakes, observe animal behaviour
Preparation – construction of buildings and roads to withstand it, training emergency services, setting up a
warning and information system