(MA or Ma (mega-annum) is a million years)
This animation shows the plate tectonic and paleogeographic evolution of North America from 200 million years ago to the present-day. North America was originally part of thee supercontinent of Pangea. About 200 million years ago, Pangea rifted apart. To the east of North America, the Central Atlantic Ridge [Mid-Atlantic Ridge (MAR)]
The Mid-Atlantic Ridge (MAR) is a mid-ocean ridge, a divergent tectonic plate or constructive plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, it separates the Eurasian and North American Plates, whereas in the South Atlantic it separates the African and South American Plates. The Ridge extends from a junction with the Gakkel Ridge (Mid-Arctic Ridge) northeast of Greenland southward to the Bouvet Triple Junction in the South Atlantic. Although the Mid-Atlantic Ridge is mostly an underwater feature, portions of it have enough elevation to extend above sea level. The section of the ridge that includes the island of Iceland is also known as the Reykjanes Ridge. The ridge has an average spreading rate of about 2.5 cm per year.
With the formation of North America, the North American Tectonic Plate is now colliding with the Pacific Tectonic Plate – and it's leading edge plates. The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres (40,000,000 sq mi), it is the largest tectonic plate, The north-eastern side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge. In the middle of the eastern side is a transform boundary with the North American Plate along the San Andreas Fault, and a boundary with the Cocos Plate. The south-eastern side is a divergent boundary with the Nazca Plate forming the East Pacific Rise ....
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Seismic Hazard Maps for the National Building Code of Canada – past ...
Boy, you can say that again!*** - Stan G, Webb
*egg·head ˈeɡˌhed/ noun
- a person who is highly academic or studious; an intellectual.