Why do earthquakes usually occur at plate boundaries?

Earthquakes happen when rock below the Earth's surface moves abruptly. Usually, the rock is moving along large cracks in Earth's crust called faults. Most earthquakes happen at or near the boundaries between Earth's tectonic plates because that's where there is usually a large concentration of faults.

Explanation:

the number of protons in the nucleus of a given element. has slight luster and conducts electricity at high temperatures like metal.but like a nonmetal,boron is brittle and does not conduct electricity well at low temperatures. in graphite, carbon is a soft,brittle solid.it is reflective,ductile,or malleable.