The jewel-like colors of the Morning Glory Pool are natural, produced by growths of different varieties of algae. As the super-heated water rises from deep within the earth it cools near the surface. The cooling creates a range of water temperatures that encourage different types of algae to grow in this mineral-rich water. Years ago the center of the Morning Glory Pool was a unique bright blue that reminded people of the Blue Morning Glory flower. Visitors to Yellowstone threw in debris over the decades which collected in the openings at the bottom of the pool and eventually restricted the flow of water. This blockage has allowed the pool to cool a few degrees. The altered temperature changed the type of algae present and the resulting colors we see today. It is now illegal to throw anything into the geothermal pools at Yellowstone but the damage has already been done to The Morning Glory Pool. The white ring around the pool is created by minerals from the water.