Amazing Geological Oddities
Update! I've taken some of your suggestions and feedback and written part 2 of Amazing Geological Oddities! See it here: Amazing Geological Oddities Part II
Moving Rocks at the Racetrack Playa, Death Valley California.
Death Valley in California is home to rocks that seem to move on their own. Pebbles to Boulders are found scattered around the "racetrack" with trails that turn, loop, and zigzag behind them. Some of the Rocks move, others don't. It was thought for some time that magnetic forces were the cause of the phenomena. Scientists now believe that the cause is wind. When there has been enough water to soak the flat clay, and temperatures lower below freezing, it causes tiny ice crystals to form. When the surface of a rock is slick enough in these conditions wind will actually have enough power to move them around, leaving a trail. 
The Richat Structure, or "Eye of the Sahara."
This spectacular landform in Mauritania in the southwestern part of the Sahara desert is so huge with a diameter of 30 miles that it is visible from space. The formation was originally thought to be caused by a meteorite impact but now geologists believe it is a product of uplift and erosion. The cause of its circular shape is still a mystery.
The driest place on Earth, Atacama Desert.
The Atacama Desert receives less than 1mm of rain per year, and at one point not a single drop of precipitation landed on its dry surface for 400 years. It's caused by the Andes rainshadow; meaning that the trade winds moving east along South America lose all moisture when they slam against the steep slopes of the Andes Mountains. The Atacama Desert is found nestled up against the western slopes of the mountain range. Interestingly, several thousand miles south the winds change direction, and the deserts are then found on the eastern side of the Andes, such as the Monte Desert in Argentina.
The Naica Mine, Cave of Crystals, Mexico.
These caverns found in a mine in Chihuahua Mexico
are home to some of the largest crystals ever discovered and are an impressive sight. The crystals are made mainly of Gypsum, and under these extremely rare conditions were allowed to grow unimpeded.
The Curtain of Fire, Hawaii.
These amazing lava fountains erupted during the first stage of the Puu Oo eruption in January, 1983. The lava created a wall of magma 100-160 feet high along a fissure along the Eastern Rift of Mount Kilauea.
Sinkholes
What could be more terrifying than the earth opening itself and swallowing your entire home? Among other places, this can become a reality in the Southeastern United States. Sinkholes are found in regions of Karst Topography, where pockets of loose sedimentary rock found under the surface can be eroded by groundwater, leaving behind caverns and caves, some of which collapse.
Stone Forest, Southwest China.
The Shilin (Chinese for stone forest) is an impressive example of karst topography. The rocks are made of limestone and are formed by water percolating the ground's surface and eroding away everything but the pillars.
The Richat Structure, or "Eye of the Sahara."
This spectacular landform in Mauritania in the southwestern part of the Sahara desert is so huge with a diameter of 30 miles that it is visible from space. The formation was originally thought to be caused by a meteorite impact but now geologists believe it is a product of uplift and erosion. The cause of its circular shape is still a mystery.
The driest place on Earth, Atacama Desert.
The Atacama Desert receives less than 1mm of rain per year, and at one point not a single drop of precipitation landed on its dry surface for 400 years. It's caused by the Andes rainshadow; meaning that the trade winds moving east along South America lose all moisture when they slam against the steep slopes of the Andes Mountains. The Atacama Desert is found nestled up against the western slopes of the mountain range. Interestingly, several thousand miles south the winds change direction, and the deserts are then found on the eastern side of the Andes, such as the Monte Desert in Argentina.
The Naica Mine, Cave of Crystals, Mexico.
These caverns found in a mine in Chihuahua Mexico
are home to some of the largest crystals ever discovered and are an impressive sight. The crystals are made mainly of Gypsum, and under these extremely rare conditions were allowed to grow unimpeded.
The Curtain of Fire, Hawaii.
These amazing lava fountains erupted during the first stage of the Puu Oo eruption in January, 1983. The lava created a wall of magma 100-160 feet high along a fissure along the Eastern Rift of Mount Kilauea.
Sinkholes
What could be more terrifying than the earth opening itself and swallowing your entire home? Among other places, this can become a reality in the Southeastern United States. Sinkholes are found in regions of Karst Topography, where pockets of loose sedimentary rock found under the surface can be eroded by groundwater, leaving behind caverns and caves, some of which collapse.
Stone Forest, Southwest China.
The Shilin (Chinese for stone forest) is an impressive example of karst topography. The rocks are made of limestone and are formed by water percolating the ground's surface and eroding away everything but the pillars.