Science Homework Help!?

10. How are volcanoes formed at divergent plate boundaries?


11. How are volcanic arcs formed?


12. How are island arcs formed?





Choose basaltic or granite


1. ___ contains a low percentage of silica


2. ___ has high viscosity


3. ___ contains a high percentage of silica


4. ___ has low viscosity


5. ___ flows quietly without explosive eruptions


6. ___ traps gases and produces explosive eruptions





batholith, dike, dome, sill


10. Magma cools slowly and solidifies before reaching the surface. _____


11. Magma is forced into a crack that cuts across rock layers. ____


12. Magma is forced into a crack parallel to rock layers. ____


14. A mass of think, highly viscous lava piles up instead of flowing freely. ____|||10.Places where plates are coming apart are called divergent boundaries. As the plates separate along the boundary, the block between the faults cracks and drops down into the soft, plastic interior (the asthenosphere). The sinking of the block forms a central valley called a rift. Magma (liquid rock) seeps upward to fill the cracks. In this way, new crust is formed along the boundary. Earthquakes occur along the faults, and volcanoes form where the magma reaches the surface.





11.formed by plate tectonics as an oceanic tectonic plate subducts under another tectonic plate and produces magma.





12.There are two ways in which a group of islands can form.


a.) As a lithospheric slab is being subducted, the slab melts when the edges reach a depth which is sufficiently hot. Hot, remelted material from the subducting slab rises and leaks into the crust, forming a series of volcanoes. These volcanoes can make a chain of islands called an "island arc". Examples of island arcs are the Japanese islands, the Kuril Islands, and the Aleutian Islands of Alaska, shown here.


Island Arcs are formed on the opposing edge of a subducted slab. For each case, there is an associated subducting slab and a trench.


b) The second way in which islands are formed is via plumes or hot spots in the lithosphere. The Hawaiian Islands are an example of this type of island formation. In this case, there is no associated subducting slab.








1. granite


2.basaltic


3. basaltic


4.granite


5.basaltic


6.granite





10. batholith


11.dike


12. sill


14. dome