My Blogs (olelog) are mainly based on my daily reading of earth science news.
Here on whatonearth.olehnielsen.dk I try to weave some of the pieces together to a greater whole with added background info.
which splits nearly the entire Atlantic Ocean north to south, is probably the best-known and most-studied example of a divergent-plate boundary. The rate of spreading along the Mid-Atlantic Ridge averages about 2.5 centimeters per year (cm/yr), or 25 km in a million years. Seafloor spreading over the past 100 to 200 million years has caused the Atlantic Ocean to grow from a tiny inlet of water between the continents of Europe, Africa, and the Americas into the vast ocean that exists today.
The Atlantic Ocean started to form in the late Triassic Period. By Early Jurassic time (about 190 million years ago) rifting separated West Africa and the Eastern U.S. and began opening the Atlantic Ocean. By Early Cretaceous (about 120 million years ago) Africa separated from South America; and by Late Cretaceous (about 80 million years ago) North America separated from Greenland.
To the north of Iceland the Mid-Atlantic continues into the Kolbeinsey Ridge (or Kolbeinsey Rise), which is broken by the Jan Mayen Fracture Zone, a transform fault. From Jan Mayen the Ridge continues as Mohns Ridge and in the Arctic Ocean the Gakkel Ridge takes over.
Kolbeinsey Ridge is divided from Iceland by an oblique running transform fault, the Tjornes Fracture Zone. It is a slow-spreading ridge with an estimated asymmetric spreading of 10mm/year. The ridge crest is nearly bare of sediments. Kolbeinsey Ridge is cut by two major transform faults, the Spar Fracture Zone and the 70.8 Fracture Zone, and is thus divided into three segments, the Southern Kolbeinsey Ridge, the Northern Kolbeinsey Ridge, and the Central Kolbeinsey Ridge. The most active part of the ridge is the Central Kolbeinsey Ridge north of the Spar Fracture Zone.
The Mohns Ridge, in the Norwegian Greenland Sea, is one of the slowest spreading centers of the mid-ocean ridge system (8 mm/yr half rate).
The Gakkel Ridge, located in the Arctic Ocean between Greenland and
Siberia with a length of about 1800 kilometres, is the slowest spreading ridge
on earth with a rate of less than one centimeter per year.
The Eurasian, North American, and African plates meet at a triple junction at the Azores.
The 550 km long Terceira Rift on the Azores Plateau has been proposed as one of the slowest spreading centres on earth.
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