Old reefs can indicate where warmer areas were in the past. Manitoulin Island in Ontario was a reef 400,000,000 years ago. The equator passed through Canada at that time. The corals that formed the island are now extinct.
One of the oldest animal-formed reefs (549,000,000 years old) was found in Nambia. This reef was made from coral-like creatures called Cloudina. They were pencil shaped and sized. At that time, all life lived in the seas. The Nambia reef was formed over a massive stromolite-formed reef. Stomolite-formed reefs were formed by bacteria for 3,000,000,000 years.
In 2010, a huge fossil coral reef was found in the south Pacific around Lord Howe Island that was the size of the Grand Canyon. It flourished between 7,000 and 9,000 years ago. It is believed that the reef “drowned” because of rising sea levels. The water level is about 100 feet below sea level now, and has been colonized by a few corals within the last 1000 years. This reef is an example of the reef that preceded the current Great Barrier Reefs that formed as fringing reefs on large islands as sea levels rose and covered the islands.
I grew up in New Mexico which has the Sandia Mountains, White Sands, and Carlsbad Caverns. Carlsbad Caverns was formed through the 265,000,000 year old “Capitan Reef” that was formed in an inland sea. This reef was formed mostly by sponges and algae, with shell mixed in. Buried later under sediment pressure, the reef formed limestone. In Carlsbad Caverns the limestone was dissolved by sulfuric acid in a process similar to a calcium reactor. The Sandia Mountains rise 1 mile above Albuquerque and are capped by limestone from the same reef system. Sulfuric acid dissolves the limestone and creates a mineral called gypsum. This mineral is what makes White Sands, white. As the dissolved limestone dripped and water evaporated, the dissolved minerals created stalactites when the cave was active during the last ice age. If water with dissolved minerals came out of the ground at wells, the evaporating minerals would form calcium flows.
Florida has limestone hundreds of feet (sometimes thousands of feet) formed from corals and shells. Intermixed is quartz sand eroded from the Appalachian Mountains.
Here is a cut through the Nambia Reef.
The mineral gypsum formed from limestone and sulfuric acid makes White Sands National Monument.
The Sandia Mountain are 2 miles high and capped by limestone formed from an old inland reef.
Carlsbad Caverns is formed through limestone from old reefs.
The dissolved minerals also forms calcium carbonate flows where springs meat the surface. This flow created a bridge over a flowing stream.
Limestone from old reefs dissolve in acidic water to form limestone sinkholes.
Here is a sinkhole in an urban environment.
There are even sink holes in reefs formed over older reefs.
https://www.bing.com/videos/search?q=ancient+reefs&&view=detail&mid=B18DFECDBA2756B20484B18DFECDBA2756B20484&FORM=VRDGAR
https://www.bing.com/videos/search?q=ancient+reefs&&view=detail&mid=62253DD526D42C97495E62253DD526D42C97495E&&FORM=VDRVRV
https://www.bing.com/videos/search?q=white+sands+areal&&view=detail&mid=957589672BF5DF1E27FF957589672BF5DF1E27FF&FORM=VRDGAR
https://www.bing.com/videos/search?q=carlsbad+caverns+formatioin&&view=detail&mid=4895FD753483162B73794895FD753483162B7379&FORM=VRDGAR
One of the oldest animal-formed reefs (549,000,000 years old) was found in Nambia. This reef was made from coral-like creatures called Cloudina. They were pencil shaped and sized. At that time, all life lived in the seas. The Nambia reef was formed over a massive stromolite-formed reef. Stomolite-formed reefs were formed by bacteria for 3,000,000,000 years.
In 2010, a huge fossil coral reef was found in the south Pacific around Lord Howe Island that was the size of the Grand Canyon. It flourished between 7,000 and 9,000 years ago. It is believed that the reef “drowned” because of rising sea levels. The water level is about 100 feet below sea level now, and has been colonized by a few corals within the last 1000 years. This reef is an example of the reef that preceded the current Great Barrier Reefs that formed as fringing reefs on large islands as sea levels rose and covered the islands.
I grew up in New Mexico which has the Sandia Mountains, White Sands, and Carlsbad Caverns. Carlsbad Caverns was formed through the 265,000,000 year old “Capitan Reef” that was formed in an inland sea. This reef was formed mostly by sponges and algae, with shell mixed in. Buried later under sediment pressure, the reef formed limestone. In Carlsbad Caverns the limestone was dissolved by sulfuric acid in a process similar to a calcium reactor. The Sandia Mountains rise 1 mile above Albuquerque and are capped by limestone from the same reef system. Sulfuric acid dissolves the limestone and creates a mineral called gypsum. This mineral is what makes White Sands, white. As the dissolved limestone dripped and water evaporated, the dissolved minerals created stalactites when the cave was active during the last ice age. If water with dissolved minerals came out of the ground at wells, the evaporating minerals would form calcium flows.
Florida has limestone hundreds of feet (sometimes thousands of feet) formed from corals and shells. Intermixed is quartz sand eroded from the Appalachian Mountains.
Here is a cut through the Nambia Reef.
The mineral gypsum formed from limestone and sulfuric acid makes White Sands National Monument.
The Sandia Mountain are 2 miles high and capped by limestone formed from an old inland reef.
Carlsbad Caverns is formed through limestone from old reefs.
The dissolved minerals also forms calcium carbonate flows where springs meat the surface. This flow created a bridge over a flowing stream.
Limestone from old reefs dissolve in acidic water to form limestone sinkholes.
Here is a sinkhole in an urban environment.
There are even sink holes in reefs formed over older reefs.
https://www.bing.com/videos/search?q=ancient+reefs&&view=detail&mid=B18DFECDBA2756B20484B18DFECDBA2756B20484&FORM=VRDGAR
https://www.bing.com/videos/search?q=ancient+reefs&&view=detail&mid=62253DD526D42C97495E62253DD526D42C97495E&&FORM=VDRVRV
https://www.bing.com/videos/search?q=white+sands+areal&&view=detail&mid=957589672BF5DF1E27FF957589672BF5DF1E27FF&FORM=VRDGAR
https://www.bing.com/videos/search?q=carlsbad+caverns+formatioin&&view=detail&mid=4895FD753483162B73794895FD753483162B7379&FORM=VRDGAR