The Earth's structure and plate tectonics. The Earth is made up of different layers: The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron and ...

Plate boundary volcanism. Volcanic activity occurs at two types of plate boundaries: mid-ocean ridges and subduction zones. At mid-ocean ridges, basaltic eruptions produce new sea-floor crust. These underwater eruptions don't produce big mountainous volcanoes, which is why they are often overlooked as the most volcanically active features on Earth.

Introduction. Subduction zones form where a plate with thinner (less-buoyant) oceanic crust descends beneath a plate with thicker (more-buoyant) continental crust. Two parallel mountain ranges commonly develop above such a subduction zone – a coastal range consisting of sedimentary strata and hard rock lifted out of the sea (accretionary wedge), and a volcanic …

Nov 17, 2011 · PLATE TECTONICS. The theory of plate tectonics describes the motions of earth’s lithosphere, or outermost layer of hard, solid rock, over geologic time. Plate tectonics provides scientists with a great deal of information about the polar region’s past. ... a lava dome has been forming inside the crater of the volcano. Composite Volcano: A ...

By the large-scale process of plate tectonics, about twelve plates, which contain combinations of continents and ocean basins, have moved around on the Earth's surface through much of geologic time. The edges of the plates are marked by concentrations of …