Tectonics
EARTH
LARGEST AND SMALLEST TECTONIC PLATES
The Earth’s rocky outer shell is broken into large
pieces called “plates”, which constantly move.
The Pacific plate (1) is more than 103,000,000 km^2
(39,768,522 sq mi) in area. It is moving north-west
in relation to North America around 7 cm (2.75 in)
per year, as measured around the Hawaiian islands.
The North Galápagos microplate (2) is in the Pacific
Ocean, off the west coast of South America. Only
around 1,559 km^2 (602 sq mi) in size, it sits at the
junction of the Nazca, Cocos and Pacific plates. LONGEST RIFT SYSTEM
Rift valleys form when Earth’s plates pull apart.
The East African Rift System is around 4,000 mi
(6,400 km) long – almost as long as the Amazon
River – with an average width of some 30–40 mi
(50–65 km). It runs from Jordan to Mozambique.
The escarpments at the valley’s edge have an
average height of 600–900 m (1,968–2,952 ft).
It has been forming for some 30 million years, as
the Arabian Peninsula has separated from Africa.Most of Earth’s geological activity occurs at the points where
tectonic plates come together or divide.MOST RECENT SUPERCONTINENT
In the distant past, tectonic plate movement
combined Earth’s continental crust into one
landmass – a supercontinent. There have been
perhaps seven in all; each one broke up due to the
same tectonic processes that created them. This
last happened some 300 million years ago, when
the crust gathered in the southern hemisphere to
create the supercontinent that we call Pangea.Three types of plate boundaries:Tectonic plates slide sideways
past each otherThe plates slide apart The plates slide towards each otherTransform Divergent ConvergentWidest continental shelf
Continental shelves are an extension of coastal
plains and are characterized by broadly sloping
submerged plains. Around 7.4% of the world’s
ocean surface sits above continental shelves.
The widest one extends 1,210 km (750 mi) off the
coast of Siberia, Russia, into the Arctic Ocean.Largest continental collision zone
Some 40–50 million years ago, the Indian
subcontinent collided with the Eurasian
continent. The impact, which is stillongoing along a zone roughly 2,400 km (1,490 mi)
in length, created the Himalayan mountains.
Nanga Parbat, a mountain in Pakistan, began
forming when this continental collision occurred.
It is the fastest-rising mountain, growing taller
at a rate of 7 mm (0.27 in) per year.Fastest-moving strike-slip fault
New Zealand’s Alpine Fault runs along most of
South Island and marks the point where the
Pacific and Australian plates meet. These plates
are moving relative to each other in a strike-slipLARGEST OPHIOLITE
Ophiolites are formed by tectonic activity that
lifts sections of Earth’s oceanic crust above
sea level and sometimes places them into the
continental crust. The Semail ophiolite in Oman’s
Hajar Mountains measures around 550 x 150 km
(341 x 93 mi) and covers an area of approximately
100,000 km^2 (38,610 sq mi). It formed around
96–94 million years ago, in the Late Cretaceous
period, and is rich in
copper and chromite.
The inset picture
provides a close-up of
“pillow lavas” at this
location – rounded
shapes of lava that
originally formed
underwater.HIGHEST EARTHQUAKE
DEATH TOLL IN MODERN TIMES
At 21:53 Coordinated Universal Time (UTC)
on 12 Jan 2010, a magnitude-7 quake struck
with an epicentre around 25 km (15.5 mi) west
of the Haitian capital Port-au-Prince. Haiti’s
government later put the death toll at 316,000,
although lower estimates put the figure at
100,000. Some 1.3 million people were displaced
by the earthquake and 97,294 houses destroyed.2
1
Q: We live at the top of
Earth’s crust. How far
below the surface does
it extend for?
A: Around 70 km (44 mi)