Pangaea's separation animated
In Iceland the Mid-Atlantic Ridge passes across the Þingvellir
National Park, a popular destination for tourists
The Mid-Atlantic Ridge includes a deep rift valley
that runs along the axis of the ridge along nearly its entire length. This rift marks the actual boundary between adjacent tectonic plates, where magma
from the mantle
reaches the seafloor, erupting as lava
and producing new crustal
material for the plates.
Near the equator
, the Mid-Atlantic Ridge is divided into the North Atlantic Ridge and the South Atlantic Ridge by the Romanche Trench
, a narrow submarine trench with a maximum depth of 7,758 m (25,453 ft), one of the deepest locations of the Atlantic Ocean. This trench, however, is not regarded as the boundary between the North and South American Plates, nor the Eurasian and African Plates.
The islands on or near the Mid-Atlantic Ridge, from north to south, with their respective highest peaks and location, are:
Northern Hemisphere (North Atlantic Ridge):
- Jan Mayen (Beerenberg, 2277 metres (7470') (at 71°06′N 08°12′W), in the Arctic Ocean
- Iceland (Hvannadalshnúkur at Vatnajökull, 2109.6 metres (6921') (at 64°01′N 16°41′W), through which the ridge runs
- Azores (Ponta do Pico or Pico Alto, on Pico Island, 2351 metres (7713'), (at 38°28′0″N28°24′0″W)
- Saint Peter and Paul Rocks (Southwest Rock, 22.5 metres (74'), at 00°55′08″N29°20′35″W)
Southern Hemisphere (South Atlantic Ridge):
- Ascension Island (The Peak, Green Mountain, 859 metres (2818'), at 07°59′S14°25′W)
- Saint Helena (Diana's Peak, 818 metres (2684') at 15°57′S 5°41′W)
- Tristan da Cunha (Queen Mary's Peak, 2062 metres (6765'), at 37°05′S 12°17′W)
- Gough Island (Edinburgh Peak, 909 metres (2982'), at 40°20′S 10°00′W)
- Bouvet Island (Olavtoppen, 780 metres (2560'), at 54°24′S 03°21′E)
The submarine section of the Mid-Atlantic Ridge close to southwest Iceland is known as the Reykjanes Ridge
. The Mid-Atlantic Ridge runs through Iceland where the ridge is also known as the Neovolcanic Zone
. In the north of Iceland the Tjörnes Fracture Zone
connects Iceland to the Kolbeinsey Ridge
Basaltic rocks of the Mid-Atlantic Ridge observed by the Hercules ROV
during the 2005 Lost City
The ridge sits atop a geologic feature known as the Mid-Atlantic Rise
, which is a progressive bulge that runs the length of the Atlantic Ocean, with the ridge resting on the highest point of this linear bulge. This bulge is thought to be caused by upward convective forces in the asthenosphere
pushing the oceanic crust
. This divergent boundary first formed in the Triassic
period, when a series of three-armed grabens
coalesced on the supercontinent Pangaea
to form the ridge. Usually, only two arms of any given three-armed graben become part of a divergent plate boundary. The failed arms are called aulacogens
, and the aulacogens of the Mid-Atlantic Ridge eventually became many of the large river valleys seen along the Americas
(including the Mississippi River
, Amazon River
and Niger River
). The Fundy Basin
on the Atlantic coast of North America between New Brunswick
and Nova Scotia
is evidence of the ancestral Mid-Atlantic Ridge.
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Last edited on 11 July 2021, at 10:59
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