Thread by @MiningNS

We love getting questions about mining, minerals and geology! We were asked why volcanoes often form along tectonic plate boundaries:
The Earth’s surface is made up of a dozen large tectonic plates and a number of smaller ones.
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These plates move imperceptibly - a few centimetres per year - and over the course of millions of years continents and oceans move and change shape. The plates pulling apart cause fractures or deep rifts in the Earth’s crust, both on land and under the sea...
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...and plates colliding with each other form mountain ranges and new islands as the rock is forced upwards. It’s this powerful tectonic activity that results in so many volcanoes at plate boundaries.
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In fact, it's estimated that 60% of all active volcanoes occur at the boundaries between tectonic plates.
The two types of plate boundaries that are most likely to produce volcanic activity are:
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Divergent Plate Boundaries - At a divergent boundary, tectonic plates move away from one another, creating gaps through which magma (melted rock) can vent.
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The plates never really separate because magma continuously moves up from the mantle into this boundary, building new plate material on both sides of the plate boundary.
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Convergent Plate Boundaries - At a convergent plate boundary, tectonic plates move toward one another and collide. Oftentimes, this collision forces the denser plate edge to subduct, or sink beneath the other plate's edge.
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As the denser plate edge moves downward, the pressure and temperature surrounding it increases, melting rock in the mantle that can rise to the surface as part of a volcano.
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Many parts of Nova Scotia are rock formed from lava from ancient volcanoes, including Cape Forchu in #Yarmouth County, #DigbyNeck, the #NorthMountain and much of southeastern Cape Breton including #Louisbourg.
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