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вигляді пластів
lens-shaped magma chambers – protuberance – виступ,
магматичні вогнища у вигляді опуклість
лінз
surge upward – stack one atop the other –
підніматись,просуватись догори укладати одна на іншу
(вверх)
seafloor spreading – поширення pulselike burst –
океанічного дна пульсуючий вибух

Task 3. Answer the questions.

The Nature and Formation of Oceanic Crust
An interesting aspect of oceanic crust is that its thickness
and structure are remarkably consistent throughout the entire
ocean basin. Seismic soundings indicate that its thickness averages
only about 7 km. Furthermore, it is composed almost entirely of
mafic (basaltic) rocks that are underlain by a layer of the
ultramafic rock peridotite, which forms the lithospheric mantle.
Although most oceanic crust forms out of view, far below sea
level, geologists have been able to examine the structure of the
ocean floor firsthand. In such locations as Newfoundland, Cyprus,
Oman, and California, slivers of oceanic crust have been thrust
high above sea level. From these exposures, and core samples
collected by deep-sea drilling ships, researchers conclude that the
ocean crust consists of four distinct layers:
 Layer 1: The upper layer is a sequence of unconsolidated
sediments. Sediments are very thin near the axes of oceanic
ridges but may be several kilometers thick next to continents.
 Layer 2: Below the layer of sediments is a rock unit composed
mainly of basaltic lavas that contain abundant pillowlike
structures called pillow basalts.
 Layer 3: The middle, rocky layer is made up of numerous
interconnected dikes having a nearly vertical orientation, called

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