Questions 45-48 are based on the following passage.

    The earth's crust is split into a number of tectonic plates that float above the hot magma liquid. The plates keep moving. This is called a tectonic plate, and the trigger for earthquakes.

    Strong earthquakes occur when two tectonic plates collide with each other. As a result, the high tension arises at the edges of the two plates. The power continues to increase and it eventually reaches an optimal point. When that energy is released an earthquake occurs.

    There are also two plates that collide and squeeze each other in the coastal area of Japan. The edges of these tectonic plates are finally pressed to the earth. A curved plate is released under another plate with a higher density. If the pressure caused by the collision of the tectonic plates is released suddenly, then a natural disaster occurs in the form of a huge earthquake.

    The earthquake has also threatened the west coast of the United States. The two plates rub against an area called the San Andreas Fault. The length of the rubbing plate is about 1.000 kilometers. The resulting friction also causes collisions. The two plates are currently sliding past each other. Since the fault is formed by natural disasters that can occur anytime.

    Tectonic plates on the surface of the earth always move dynamically so that earthquakes often occur at the edge of each plate. The most famous earthquake area is the Pacific fire ring which stretches from Chile in South America across the eastern coast of North America, Japan, the Philippines, Indonesia to the Tonga Island.

What is the main idea of the passage?