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2. Convergent boundaries.
TEXT 2

Task 1. Read the text and translate it into Ukrainian (in written form). Build up a
list of key terms to the text.

Changing boundaries
Although the total surface area of Earth does not change, individual plates may diminish
or grow in area depending on the distribution of convergent and divergent boundaries. For
example, the Antarctic and African plates are almost entirely bounded by spreading centres and
hence are growing larger. By contrast, the Pacific plate is being subducted along much of its
perimeter and is therefore diminishing in area. At the current rate, the Pacific would close
completely in 300 million years— but this is unlikely because changes in plate boundaries will
probably occur before that time.
New plate boundaries are created in response to changes in the forces acting on the
lithosphere. For example, a relatively new divergent boundary is located in Africa, in a region
known as the East African Rift Valleys. If spreading continues in this region, the African plate
will split into two plates, separated by a new ocean basin. At other locations plates carrying
continental crust are moving toward each other. Eventually these continents may collide and be
sutured together. Thus, the boundary that once separated these plates disappears, and two plates
become one. As long as temperatures within the interior of our planet remain significantly higher
than those at the surface, material within Earth will continue to circulate. This internal flow, in
turn, will keep the rigid outer shell of Earth in motion. Thus, while Earth’s internal heat engine is
operating, the positions and shapes of the continents and ocean basins will change and Earth will
remain a dynamic planet.

Task 2. Answer the questions:
1. How are boundaries changing?
2. Will Earth remain a dynamic planet?

Test yourself

Task: Tell whether the sentences are true or false. Correct the false ones.
1. Six major lithospheric plates are recognized.
2. Several large plates include an entire continent. None of the plates is defined entirely by the
margins of a single continent.
3. The titanic movements of Earth’s lithospheric plates generate earthquakes and create
volcanoes.
4. Divergent boundaries - where plates move together, resulting in the subduction
(consumption) of oceanic lithosphere into the mantle.
5. Convergent boundaries - where plates move apart, resulting in upwelling of material from
the mantle to create new seafloor.
6. Plate margins where oceanic crust is being consumed are called a deep-ocean trench.
7. New plate boundaries are created in response to changes in the forces acting on the
lithosphere.
8. As long as temperatures within the interior of our planet remain significantly lower than
those at the surface, material within Earth will continue to circulate.
9. While Earth’s internal heat engine is operating, Earth will remain a dynamic planet.

UNIT 6