When two tectonic plates rub together, it's called a transform fault boundary. This kind of boundary is where plates slide horizontally past each other. Here's what happens:

* Friction: The plates are constantly pushing against each other, creating friction. This friction generates a lot of heat and pressure.

* Earthquakes: The pressure from the friction builds up until it's released suddenly. This release causes earthquakes. These earthquakes can be small and barely noticeable, or they can be massive and devastating.

* Fault Lines: The area where the plates slide past each other is called a fault line. These fault lines are visible on the Earth's surface as cracks or fractures.

* No Volcanoes: Unlike convergent boundaries where plates collide and create mountains and volcanoes, transform boundaries don't typically result in volcanic activity.

Famous Examples:

* San Andreas Fault: This fault runs along the coast of California and is a prime example of a transform fault boundary. It's responsible for many earthquakes in California, including the devastating 1906 San Francisco earthquake.

* North Anatolian Fault: This fault runs through Turkey and is responsible for many major earthquakes, including the 1999 Izmit earthquake.

In Summary:

When tectonic plates rub together at a transform fault boundary, it causes friction, leading to the accumulation of pressure and the release of that pressure in the form of earthquakes. This interaction also creates visible fault lines on the Earth's surface.