In Canada, there is an area with less gravity than everywhere on Earth Bashny.Net

In 1960, when scientists began to study the Earth's gravitational field, it was assumed that gravity should be the same everywhere on the planet, but discovered that it can vary depending on the location. For example, in Canada, there are some areas where gravity is less - in particular, near Hudson Bay.

According to one theory, the reason for this is the convection in the mantle. Mantle - a layer of the expanded rock, called magma, located about 100-200 km beneath the earth's surface. The temperature of the magma is extremely high, and due to the constant movement that we, being on the surface, do not feel, it creates convection currents. Convection moves the lithospheric plates closer to the center of the Earth, which reduces the weight of the rocks in this area and, as a result, and gravity.

According to another version, the reason Lavrentid ice sheet, which had previously covered a significant part of modern Canada and the northern United States. The thickness of the ice cover on average reached 3, 2 km away, and in two areas of Hudson Bay - 3, 7 km away. This area of ​​the glacier was previously very difficult. 10,000 years ago Lavrentid melted, leaving a deep hollow in the earth. To better imagine what happened, imagine a bread crumb on which you are pushing down with your finger. The bread is formed fossa. If you remove your finger, then after a short time and the pit disappear. Roughly the same thing happens in the case of Hudson Bay. It should, however, take into account the fact that the Earth's surface is reduced very slowly, about 1, 5 cm per year, and the area is now Hudson Bay has less mass as before equilibrium is achieved at the expense of the ice sheet, now disappeared. And if weight is less - and less gravity.

via factroom.ru