Earth's core temperature is about 10,800 degrees Fahrenheit. If it cooled down then there would be no earthquakes or volcanoes. Why? No heat means all the active volcanoes would suddenly become extinct. Also, earthquakes occur when tectonic plates rub against each other. These plates move because of the intense heat coming from the core. Now, no heat from the core means no movement of tectonic plates, thus no earthquakes. Scientists believe that earth's heated core plays an important role in the creation of its magnetic field. With no magnetic field, the following things will occur. Our atmosphere will slowly but surely disappear as there will be no protection from harmful solar winds. Also, migratory birds would have a very hard time finding their destination.