What causes hawaii to have volcanoes?

Hawaiian plumes and the hotspot activity.

Explanation:

As volcanoes are created by the collision of the two plate boundary the Hawaiian volcano is a result of the Hotspots created by the sudden shift and movements in the Pacific plates.  The presence of the magma chambers induces this hotspot activity and as this slowly increases over time make the volcanoes active and these are formed by the convective cells that originate from the mantel of the earth.

I'm pretty sure there's a geometry rule for   anyways, if the triangle is equilateral, and the circle is circumscribed, the circle is outside of the triangle.  to find the area, you need the radius.  the radius should be a straight line from the center of the triangle to any of it's points.  draw lines from the center of the circle to each of the triangle points.  draw three more lines from the center to the middle of the sides of the triangle.  you should now have six separate 30-60-90 triangles inside of your original triangle. use your 30-60-90 rules to solve for the radius, then the circumference. 

Geologists use  seismic waves to  locate an earthquake's epicenter..