If all convection currents on Earth stopped that would be a natural disaster. The amount of heat which the sun radiates at us sets the temperature of the Earth's surface. If it weren't for convection, then the North and South poles would be even colder and the equator even hotter. Oceanic currents like the Gulf Stream bring warm water further north, and currents like the California current bring cold water towards the equator. So if convection completely stopped the high and low temperatures would force people and animals to move away from the poles and equator.

Most of the rocks in the earth convect at a large scale. Even though they are solid they can still move slowly, a little like putty. Convection can even help form large islands like Hawaii and Samoa in the Pacific Ocean. If the rocks stopped flowing inside the Earth we would eventually not have any new volcanoes on islands as well!

If all the convective currents stopped, Earth would become a very different place than we know it today. If Earth had no convective currents, that would mean the inner Earth has solidified, therefore, we would not have plate tectonics. Our Earth’s crust is made up of plates of varying sizes that move very slowly around the planet over time, this theory is called Plate Tectonics. Plate tectonics create many of the geologic features we see on Earth today, such as volcanoes and mountain ranges. These geologic features play a huge role in regulating the earth’s climate; if these features ceased to exist, our climate would become intolerable to life. We humans would not be able to exist. Eventually the landscape would flatten out from the simultaneous lack of mountain building from colliding tectonic plates and from erosion of existing mountain ranges. The planet would likely become desert-like. Even scarier is that, chaotic convective motions in the outer core of Earth are what maintain our magnetic field! If these convective motions were to stop, we would loose our magnetic field, which is our ultimate protection from the sun’s harmful radiation (this is what causes sunburns), as our ozone layer (the layer of our atmosphere that protects Earth from the sun’s ultraviolet radiation) would deteriorate.

That's not possible, but if somehow, magically, it did, then anybody not living in a desert would be baked to death by the greenhouse effect (because water vapor is a greenhouse gas). There would be no more weather. Plate tectonics and volcanoes would also stop.

First let's identify the main convection currents on the earth. Convection is the circulation (and mixing) of gases or liquid. On earth, this happens in air (which causes our weather), and in ocean currents. If for some reason convection stopped, air would not circulate, and weather would stop. Air wouldn't flow over the waters, suck up moisture and then rain it out on land. Without this rain, all plants and crops would die. The movement of weather systems is also how warm air at the equator moves and gives heat to the poles. Without the movement of this warm air, northern countries like Canada would be even colder. The movement of water in our oceans also pushes warm water at the equator to the poles. These water currents also move nutrients. Without the convection of the oceans, and the currents to move the nutrients, most of our marine animals and plants would die.

It's a good thing we still have convection to keep us all alive! This is a great example of a simple scientific principle can explain some big ideas.