Some
questions to practice under geophysics
1. Write vividly on the theory of continental
drift.
The continental drift refer to the
phenomena of gradual movement of the earth through geological time, first
developed by alfred wegner in about 1912, he was the first to collect evidence
to support the displacement of the continental shelves.
according to alfred wegner all the
landmasses where grouped in the late paleozoic.
He call called pangeae and he envisioned that it it surrounded by a
single sea, meaning single supercontinent surrounded by a single water body.
Over time the supercontinent split along the east-west line into laurasia in the north and gondwana in the
south, the laurasia comprises of north america, the greenland europe and most of asia while the gondwana comprises of
south america, africa, australia, india and antarctica.
Kontinentalverschiebang is a term use to refer to split of the supercontinent
along a horizontal line.
Laurasia and gondwana were initially joined by the crustal brigde linking
north america and laurasia , this crustal bridge become tenuous as the earlier tethey’s
sea opened along the line the mediterranean . The caribbean was created by the
rifting of the americas. Laurasia drifted northward and gondwana continue to split. The splitting of the laurasia led to the birth
of the atlantic oceans.
For about 70 million years ago, the gap between continent is still narrow
and intercontinental movement between land animals was possible.
60 million years ago , continent are still in their present position ,
but up to date tectonic movement is still going on.
Evidence for this tectonic movement or continental drift is that similar
plant and animals fossils were found in the continent. The complementary arrangement of facing side
of africa and america is obvious, the distribution of carboniferous in several part of the world is also an
evidence.
2. Discuss sea floor spreading: sea
floor spreading
The idea of sea floor spreading were proposed by dietz and hess in the
mid of 20th century oceanographers and marine geologist has observed
that there is an mountain ranges twist protrude and branches into the word
oceans, and that this features are young and much young toward the centre. This
reveals that there is volcanic eruption and earthquakes are associated with it.
According to vine and mathew if the molten rocks are were erupted along
the along the axis of mid ocean ridge, it would pick up same magnetic field as
it cooled. If the cooled rocks are subsequently pushed down along the ridge it
will form strips of alternately magnetized rocks.
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