Tectonic plates – divergent, convergent and transform boundaries; earthquakes and volcanoes
GeographyEarth's Structure & LandformsAges 11–12
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Earth's Structure & Landforms
A cross-section of two tectonic plates drifting on a mantle with convection currents. Choose a boundary type: plates moving apart (magma rises to form a mid-ocean ridge and new oceanic crust), plates colliding (an oceanic plate subducts beneath a continental plate, producing earthquakes, volcanoes and high mountain ranges) or plates sliding past each other (a transform fault, producing earthquakes). Drag a plate by hand or press Run to move the plates at their real speed of a few centimetres per year; the number of years elapsed and the distance moved are shown. The top-right panel shows a cross-section of Earth's layers at true depth. Two more views: Volcano types (basaltic, andesitic or rhyolitic magma and its gas content give shield volcanoes, cinder cones, composite volcanoes, lava domes or calderas, with lava flows, ash, pyroclastic flows, lahars and stratospheric aerosols) and Earthquake (focus and epicentre, P, S and surface waves, three seismograms and a hillside that may slide). Magnetic stripes view: lava cooling at a mid-ocean ridge records the direction of Earth's magnetic field, which reverses on the real polarity timescale, so stripes of normal and reversed polarity grow symmetrically on both sides of the ridge. Sail a magnetometer ship across them to draw the anomaly profile, read the sea-floor age and heat flow from drill cores, record a table and compute the spreading rate = distance ÷ age.
Lesson: Structure of the Earth; tectonic plates; earthquakes and volcanoes
What it shows
Earth's rigid outer shell, the lithosphere, is broken into plates that move a few centimetres per year, driven largely by convection in the hot mantle beneath. What happens at a plate boundary depends on the relative motion. At divergent boundaries, rising magma creates new oceanic crust and a mid-ocean ridge. At convergent boundaries, the denser oceanic plate subducts, forming a deep trench, volcanoes and fold mountains. At transform boundaries, plates slide past each other along a fault, building up strain that is released in earthquakes. A second panel shows the crust, mantle and core at their true relative depths. Two more views link boundaries to hazards: magma silica and gas decide whether a volcano erupts gently or explosively, and an earthquake's focus depth and magnitude decide how strongly the ground shakes. The Magnetic stripes view shows the evidence for sea-floor spreading: symmetric bands of normal and reversed magnetisation on both sides of the ridge that match the reversals of Earth's field.
How to use
Choose a Plate boundary type, press Run and watch the counter of years elapsed and distance moved. Compare what forms at each boundary: bands of new crust, a trench and volcano, or an offset river and road. Change the Plate movement speed and the Simulation speed to see how a few centimetres per year add up to hundreds of kilometres over millions of years. Keep the mantle convection currents on to link surface motion to its cause. On the Volcano types tab, change the Magma and Gas content; on the Earthquake tab, drag the focus and read the S − P lag in the table. On the Magnetic stripes tab, drag the ship or press Auto traverse, press Record at several distances and divide distance by age; tick Hide the rate (unknown) to test yourself.
Parameters you can change
- Plate boundary type Plates moving apart, Plates colliding, Plates sliding past each other
- Plate movement speed 1–15 cm/year
- Simulation speed 10000–2000000 years/second
- Show cross-section of Earth's layers
- Show mantle convection currents
- View Plate boundaries, Volcano types, Earthquake, Magnetic stripes
- Magma type Basaltic, Andesitic, Rhyolitic
- Gas content of the magma 0.5–6 % by mass
- Snow and ice on the summit
- Focus (hypocentre) depth 5–700 km
- Moment magnitude Mw 4–9.5
- Hillside soaked by heavy rain
- Hide the spreading rate (random unknown)
Questions to explore
- At which type of boundary is new oceanic crust created, and where does the new material come from?
- How far does a plate moving 5 cm per year travel in one million years?
- Why do plates sliding past each other cause earthquakes but very few volcanoes?
