Avariety of pear tree, known as bradford, was
originally introduced into the eastern united
states in the 1960s. today, this tree is crowding
out other plants in these states. this situation
best illustrates
(1) an unintentional negative effect of altering
an ecosystem
(2) how a foreign species is controlled in the
eastern united states
(3) that the introduction of a foreign species
does not affect food webs
(4) that serious environmental consequences
can be avoided by importing a foreign
species

Subduction zones form when an oceanic plate collides with another oceanic plate or continental plate. the continental crust is lighter and less dense than oceanic crust. continental crust's density is approximately 2.7 grams per cubic centimeter. oceanic crust is thinner and the average density is about 3.3 cubic centimeters. when the two crustal plates converge the oceanic plate always bends and subducts beneath a continental plate. once the oceanic crust subjects, the rocks are subjected to changes in heat and pressure. because of this, we would expect to find rocks in the area of a subduction. a) clastic b) igneous c) metamorphic d) sedimentary