EARTHLONGEST EARTHQUAKE
The Sumatra-Andaman Islands earthquake in the Indian Ocean, on 26 Dec
2004, was the longest-lasting ever recorded. Its duration was measured
at 500–600 sec – around 10 minutes! The magnitude-9.1–9.3 earthquake
triggered a massive tsunami (damage pictured) that devastated low-lying
regions around the Indian Ocean and caused damage as far away as Somalia.LONGEST SUBDUCTION
“Subduction” describes the movement of one tectonic plate beneath another (see
convergent plate boundary illustration, below left). The Andean Subduction Zone
runs for some 7,000 km (4,350 mi) along the western coast of South America.
Here, the denser ocean crust of the Nazca plate plunges below the lighter
continental crust of South America and is recycled in the Earth’s upper mantle.
The Mid-Atlantic Ridge
moves at 10–40 mm
(0.39-1.5 in) a year – or
about the same rate that
your fingernails grow
The Nazca plate
travels at 160 mm
(6.29 in) a year, or
about the same rate
that your hair growsTectonic plates are around
100 km (62 mi) thick – about
the same as the thickness
of the Earth’s atmosphereAtmosphereTectonic plate
Magmafault (the transform fault is one such – see left).
On 8 Mar 2016, scientists from Victoria University
of Wellington and GNS Science (both NZ) revealed
that the plates are moving 4.7 cm (1.8 in) per
year in relation to each other, and have covered
700 km (434 mi) in the past 25 million years.
Fastest seafloor spreading centre
The East Pacific Rise is a tectonic plate boundary
that runs from Antarctica to the west coast
of the USA. A portion of the East Pacific Rise
called the Pacific-Nazca boundary is pushing
the Pacific and Nazca continental plates apart
at a rate of around 15 cm (5.9 in) per year.
The slowest seafloor spreading centre is the
Gakkel Mid-Ocean Ridge, the northern extension
of the Mid-Atlantic Ridge. Separating the North
American and Eurasian plates, it runs for 1,800 km
(1,118 mi) from the north of Greenland to Siberia.
The rate of spread ranges from 13.3 mm (0.52 in)
per year near Greenland to 6.3 mm (0.24 in) per
year at the other end, close to Siberia.
Newest ocean
In 2005, a rift 56 km (34.7 mi) long opened in
the Afar Depression in Ethiopia (aka the Danakil
Depression, the lowest point in Africa). In
Nov 2009, geologists heralded it as a new ocean.
The Pacific is the oldest ocean. Some rocks on
its floor are approximately 200 million years old.Oldest evidence for plate tectonics
On 8 Jul 2002, a team of Chinese and US
geologists announced their discovery of rocks
indicating that plate tectonics were active on
Earth some 2.5 billion years ago. This is around
500 million years earlier than previously thought.FIRST...
Continent
Geological evidence suggests that there was
a single continental landmass on Earth from
3.6 billion to 2.8 billion years ago. Named Vaalbara,
it was smaller than any of today’s continents.Suggestion of continental drift
Looking at any map of Earth, it is clear that
the coastlines of west Africa and east South
America complement each other. The first
person to have noticed this is believed to have
been the Flemish mapmaker Abraham Ortelius
(1527–98). He argued that the two continents
were once joined together before being pulled
apart “by earthquakes and flood”. Continental
drift only became accepted by mainstream
academia in the second half of the 20th century.Earthquake registered from orbit
The European Space Agency’s (ESA) Gravity
Field and Steady-State Ocean Circulation
Explorer (GOCE) satellite was launched on 17 Mar- It mapped the Earth’s gravity field until
11 Nov 2013, when it re-entered the atmosphere
and was destroyed. On 11 Mar 2011, as it passed
through Earth’s ultra-thin thermosphere,
GOCE picked up weak sound waves caused by
a devastating earthquake that struck Japan.
LONGEST SUBMARINE
MOUNTAIN RANGE
The Mid-Ocean Ridge is an
underwater mountain range that
extends 40,000 mi (65,000 km)
from the Arctic Ocean to the
Atlantic Ocean, around Africa, Asia
and Australia, and under the Pacific
Ocean to the west coast of North
America. At its apex, it stands
13,800 ft (4,200 m) above the base
ocean depth – around half as tall
as Everest, the highest mountain.