Gravity in the surrounding areas, including the Hudson Bay area and Quebec, is lower than in other areas.
For more than four decades, scientists have tried to identify the causes of much of Canada's “missing” gravity, especially the Hudson Bay area. In other words, the gravity in the Hudson Bay region and surrounding areas is lower than in other parts of the world, a phenomenon first discovered in the 1960s when the Earth's gravitational field is charted.
Two theories have been proposed to explain this theory. But before we review them, it's important to first consider what creates gravity. At the base level, gravity is proportional to mass. So, if the mass of a certain area somehow becomes smaller, then gravity becomes smaller. Gravity can vary in different parts of the earth. We usually think of it as a ball, but the earth actually expands at the equator and becomes flat on the pole due to rotation. The mass of the earth does not spread proportionally, it can change its position over time. So the scientists proposed two theories that explain how the mass of the Hudson Bay area was reduced and contributed to the low gravity of that area.
One theory centers on a process known as convection that takes place in the mantle of the earth. The mantle is a layer of molten rock called magma that exists 60 to 124 miles (100 to 200 km) below the earth's surface. Magma is very hot, constantly spinning and rising and falling to make convective flow. Convection pulls down the continental plates of the earth, reducing the mass of that region and reducing gravity.
A new theory to explain the missing gravity in the Hudson Bay area is about the Laurentide Ice Sheet, which covers much of the current Canadian and northern parts of the United States. This ice sheet was almost 2 miles (3.2 km) thick in most sections, and 2.3 miles (3.7 km) thick in both areas of Hudson Bay. It is also very heavy and heats up the earth. Laurentide Ice Sheet melted for a period of 10,000 years, eventually disappearing 10,000 years ago. It left deep indentation on the earth.
To get a better idea of what happened, think about what happens when you lightly press it with your fingers or put elastic bread on the surface of the cake. Some of them move sideways and have indentation. But release your finger and it will return to normal. A similar phenomenon occurred in the Laurentide Ice Sheet. The theory suggests that the earth does not bounce so much as the earth rebounds too slowly (less than 0.5 inches per year). In the meantime, the area around Hudson Bay has less mass because part of the earth has been pushed to the side of the ice. Less mass means less gravity.
So what theory is correct? It turns out there is both. Both the convection and the rebound effect of the ice sheet cause a decrease in gravity around Hudson Bay. First of all, we will consider the ice theory.
To calculate the impact of the Laurentide Ice Sheet, scientists at the Harvard-Smithsonian Astrophysics Center used data collected by the Gravity Recovery and Climate Experiment (GRACE) satellite between April 2002 and April 2006. The GRACE satellite is 310 miles (500 km) away from the highly elaborate planet and 220 km away. The satellite can measure distances to microns, so it can detect gravity changes in gravity. As the map satellites fly over the Hudson Bay area, gravity decreases, causing the satellites to be slightly farther away from the Earth and its sister satellites. This distance shift is detected by the satellite and used to calculate the change in gravity. You can also create a gravitational field map using all detected shifts.
Using the GRACE data, scientists were able to create a topographical map that outlines the Hudson Bay of the last ice age covered with Laurentide Ice Sheet. These maps showed interesting features for the area, including two swollen areas with a lot of ice left on the west and east of Hudson Bay. Gravity is lower than other parts of the gravity depletion area.
Another important finding comes from the GRACE data. The ice sheet theory has shown that it accounts for 25-45% of the gravitational change in Hudson Bay and its surrounding areas. Subtracting the "rebound effect" from the gravity signal in the region, scientists determined that the remaining 55-75% of the gravity change was due to convection.
Hudson Bay area is less gravity for a long time. It is estimated that the Earth must rebound 650 feet or more to return to its original location, which will take about 5,000 years. But the rebound effect is still noticeable. Although sea levels are rising worldwide, sea levels along the Hudson Bay shores continue to recover due to the weight of the Laurentide Ice Sheet.
Although the mysteries surrounding Canada's gravitational anomalies have calmed down, this research has more impact. Scientists who participated in the Harvard-Smithsonian Center study were surprised to see how the earth looked 20,000 years ago. And by separating the effects of the repulsive effect of the ice sheet, we better understand how convection affects gravity and how continents change over time. Finally, Grace satellites provided scientists with data on many ice sheets and glaciers. By investigating climate change that happened thousands of years ago, scientists can better understand how global warming and rising sea levels affect the Earth today and affect our future.
For more than four decades, scientists have tried to identify the causes of much of Canada's “missing” gravity, especially the Hudson Bay area. In other words, the gravity in the Hudson Bay region and surrounding areas is lower than in other parts of the world, a phenomenon first discovered in the 1960s when the Earth's gravitational field is charted.
Two theories have been proposed to explain this theory. But before we review them, it's important to first consider what creates gravity. At the base level, gravity is proportional to mass. So, if the mass of a certain area somehow becomes smaller, then gravity becomes smaller. Gravity can vary in different parts of the earth. We usually think of it as a ball, but the earth actually expands at the equator and becomes flat on the pole due to rotation. The mass of the earth does not spread proportionally, it can change its position over time. So the scientists proposed two theories that explain how the mass of the Hudson Bay area was reduced and contributed to the low gravity of that area.
One theory centers on a process known as convection that takes place in the mantle of the earth. The mantle is a layer of molten rock called magma that exists 60 to 124 miles (100 to 200 km) below the earth's surface. Magma is very hot, constantly spinning and rising and falling to make convective flow. Convection pulls down the continental plates of the earth, reducing the mass of that region and reducing gravity.
A new theory to explain the missing gravity in the Hudson Bay area is about the Laurentide Ice Sheet, which covers much of the current Canadian and northern parts of the United States. This ice sheet was almost 2 miles (3.2 km) thick in most sections, and 2.3 miles (3.7 km) thick in both areas of Hudson Bay. It is also very heavy and heats up the earth. Laurentide Ice Sheet melted for a period of 10,000 years, eventually disappearing 10,000 years ago. It left deep indentation on the earth.
To get a better idea of what happened, think about what happens when you lightly press it with your fingers or put elastic bread on the surface of the cake. Some of them move sideways and have indentation. But release your finger and it will return to normal. A similar phenomenon occurred in the Laurentide Ice Sheet. The theory suggests that the earth does not bounce so much as the earth rebounds too slowly (less than 0.5 inches per year). In the meantime, the area around Hudson Bay has less mass because part of the earth has been pushed to the side of the ice. Less mass means less gravity.
So what theory is correct? It turns out there is both. Both the convection and the rebound effect of the ice sheet cause a decrease in gravity around Hudson Bay. First of all, we will consider the ice theory.
To calculate the impact of the Laurentide Ice Sheet, scientists at the Harvard-Smithsonian Astrophysics Center used data collected by the Gravity Recovery and Climate Experiment (GRACE) satellite between April 2002 and April 2006. The GRACE satellite is 310 miles (500 km) away from the highly elaborate planet and 220 km away. The satellite can measure distances to microns, so it can detect gravity changes in gravity. As the map satellites fly over the Hudson Bay area, gravity decreases, causing the satellites to be slightly farther away from the Earth and its sister satellites. This distance shift is detected by the satellite and used to calculate the change in gravity. You can also create a gravitational field map using all detected shifts.
Using the GRACE data, scientists were able to create a topographical map that outlines the Hudson Bay of the last ice age covered with Laurentide Ice Sheet. These maps showed interesting features for the area, including two swollen areas with a lot of ice left on the west and east of Hudson Bay. Gravity is lower than other parts of the gravity depletion area.
Another important finding comes from the GRACE data. The ice sheet theory has shown that it accounts for 25-45% of the gravitational change in Hudson Bay and its surrounding areas. Subtracting the "rebound effect" from the gravity signal in the region, scientists determined that the remaining 55-75% of the gravity change was due to convection.
Hudson Bay area is less gravity for a long time. It is estimated that the Earth must rebound 650 feet or more to return to its original location, which will take about 5,000 years. But the rebound effect is still noticeable. Although sea levels are rising worldwide, sea levels along the Hudson Bay shores continue to recover due to the weight of the Laurentide Ice Sheet.
Although the mysteries surrounding Canada's gravitational anomalies have calmed down, this research has more impact. Scientists who participated in the Harvard-Smithsonian Center study were surprised to see how the earth looked 20,000 years ago. And by separating the effects of the repulsive effect of the ice sheet, we better understand how convection affects gravity and how continents change over time. Finally, Grace satellites provided scientists with data on many ice sheets and glaciers. By investigating climate change that happened thousands of years ago, scientists can better understand how global warming and rising sea levels affect the Earth today and affect our future.
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