As I know, both divergent boundary and hot spot are formed by rise of magma of convention, but divergent boundary is a line and hot spot is a point, is there difference between 2 kinds of rising magma?
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Divergent boundaries occur at the boundary between plates. A divergent boundary is where two tectonic plates are actively being pushed apart. Divergent boundaries create rift valleys on land and eventually ridges on ocean floors, where hotter material wells up from the mantle, cools and form new crust. For example, the East African Rift Valley (a divergent boundary), is pushing apart the African plate, separating Somalia from the continent. Eventually the rift valley will flood, producing a ocean between the newly split plates with the East African Rift becoming a mid-ocean ridge.
Hot-spots, or mid-plate tectonic activity, occur away from boundaries between plates. A hot-spot is where a plate is moving over a stationary mantle plume. Hot-spots are responsible for island-chains, such as those seen in Hawaii, which form as the plate slides over the plume or even volcanoes on land, like Yellowstone. The islands of Hawaii lie thousands of kilometres away from the boundaries of the Pacific plate on which they sit. A nice feature is that the Hawaiian island chain lies in a north-westerly line that matches the direction the Pacific plate is moving.
The main thing to keep in mind is that divergent boundaries occur at the boundaries of plates. Hot-spots occur in the middle of plates, often thousands of kilometres away from the boundaries of the plates.
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1$\begingroup$ Divergent boundaries are not being pushed apart by rising magma. On the contrary, the plates are moving apart because they are pulled down at subduction zones and this creates a hole which magma rises to fill. $\endgroup$– bonJul 19, 2016 at 9:40
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1$\begingroup$ @bon, The convection cells of rising magma do cause the divergent boundaries. However, some plates move faster than the currents beneath them. There is where the gravitational pull of subduction you mentioned comes in. For example, the Nazca plate cruises eastward at 10cm while the mantle beneath flows at 5cm. This is most likely due to the pull of oceanic crust that occurs at trenches. As the plate dives into the mantle, it pulls on the portion behind it. The bigger the sunken portion becomes, the harder it pulls on the oceanic crust. $\endgroup$– G. GipJul 19, 2016 at 9:55
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1$\begingroup$ Hotspots are not plumes of magma, they are plumes of hot solid mantle material. They melt only when they get to lower pressures by decompression melting, or they don't melt at all and they heat more easily fusible crust material and melt that instead. $\endgroup$– GimelistJul 19, 2016 at 20:38