Gravity is another type of indirect evidence that geophysicists use to learn about the interior of the Earth. The force of gravity between two objects depends on the mass of the object and the distance between them. To study Earth's interior, geologists also use an indirect method. But instead of knocking on walls, they use seismic waves. When earthquakes occur, they produce seismic waves. Geologists record the seismic waves and study how they travel through Earth.
The NAFTA (North American Free Trade Agreement) is the agreement that has lowered trade barriers between Mexico and the rest of North America. It was signed January 1, 1994.
The pressure gradient is the force that is produced due to the rotation of earth pressure cells that creates lighter air to move upwards and heavier to move downwards due to the difference in densities of air.
As the air above consists of lighter elements the oceanic air mostly consist of diatomic molecules of oxygen and nitrogen thus containing a large amount of water vapor, all these molecules have a mass that are pulled down by the gravity and this pull of gravity on columns of gas applies a force what we see an atmospheric pressure.
The gas particles and molecules of heavy and denser matter get stuck at the ground, similarly, as the air cools is descends and warm air rises. Thus upwards and downward motion of air causes convergence and divergence of molecules.
