Are there any geology only related educational institutions?
Why would you limit yourself? You could just go to a regular university and enroll in the geology degree program. In some countries (like Germany) you would then only take courses necessary to become a geologist (including the math and physics you need to understand for it). In some other countries (e.g, the United States) you'd have to take other courses for "breadth requirements" as well, but most of your courses would still be in geology. 

The fact that a regular university also offers courses in other areas doesn't really matter that much, or does it?