Waltemath described one of the proposed moons as being 1,030,000 km (640,000 mi) from Earth, with a diameter of 700 km (430 mi), a 119-day orbital period, and a 177-day synodic period.
A subduction zone is formed at a convergent plate boundary when one or both of the tectonic plates is composed of oceanic crust. The denser plate, made of oceanic crust, is subducted underneath the less dense plate, which can be either continental or oceanic crust.s a result of pressure, friction, and plate material melting in the mantle, earthquakes and volcanoes are common near convergent boundaries. When two plates move towards one another, they form either a subduction zone or a continental collision. This depends on the nature of the plates involved.
1 The lithosphere is composed of the crust, and some of the upper mantle. 2  Mature oceanic plate is approximately 80-100 km thick, of which, the upper 5-7 km is oceanic crust. 3  Continental plate is somewhat thicker, perhaps 150-200 km thick, and includes continental crust which varies from 5 to 70 km in thickness. At other convergent boundaries, oceanic plate meets other oceanic plate. 2  This results in an oceanic trench and a chain of volcanic islands known as an island arc. Japan, the Philippines and the Aleutians are examples of island arcs. 3  At some convergent boundaries, two continents collide.