Within or on the edges of the spiral arms of the galaxy<span> (Like the dust clouds, </span>ionization nebulae<span> are </span>located<span> primarily within or on the edges of spiral arms. This is because spiral arms are regions of active star formation.</span>
The distribution of earthquakes defines the boundary of the earth tectonic plates as earthquakes have the seismic energy that gets transferred to the landscape and as result to this the transform, divergent and convergent boundaries along the plate margins can be found.
Deep focus earthquakes are those that have shallow bases and origin in trenches where the lands are subdued under the plates and are associated with prominent oceanic features like the mid-oceanic ridges, deep-sea ridges, and seamounts, guyots and canyons, etc.
The ocean floor of convergence that creates the deep-seated earthquake as being collided with land and an oceanic plate or being collided with an oceanic and oceanic plate boundary. Physical features are faults and rift valleys.
The tonga trench is located near the tonga island and in the southwestern pacific ocean, is the second deepest trench on earth. Pacific plate is being subdued under this tench with an in convergence rate of 15 cm/year. Thus the rigid slab of lithosphere plate is being pulled towards this zone of convergence.
