Ask an Explorer

Questions answered during the expedition are below.

 


Question from: Lance, Tolland, Connecticut
On the way out to Whalebone Bay from B.I.O.S. there is the small Lover’s Pond. It has a tidal flux and a small anemone lined opening. Is it known if this opening is associated with a larger cave system that has been explored?

Answer from: Tom Iliffe and Brett Gonzalez, Marine Biospeleology Lab, Texas A&M University
The small opening that you are referring to in Lover's Lake still remains a mystery. Since there is such an abundance of caves in Bermuda, there is a good chance that this opening could be a new system never before seen. Cave divers earlier in the year were sent to explore and try and push the system but there was little success in finding a suitable entrance or any positive leads of going passage. Further investigation is still needed to properly assess this opening. It is known that a large percentage of the water in this lake exchanges with the tides, suggesting a rather direct connection to the sea.


Question from: Lance, Tolland, Connecticut
Since the deep water caves were at one time above sea level, is there any expectation of finding terrestrial fossils that could be dated to increase our knowledge of early Bermuda ecology?

Answer from: Tom Iliffe and Brett Gonzalez, Marine Biospeleology Lab, Texas A&M University
Absolutely. Caves, both terrestrial and submerged, are great repositories of fossils which could be used to catch a glimpse of what life was like in Bermuda thousands of years ago. Admiral's Cave in Bermuda has been a study site for paleozoologists who were excavating cave dirt examining the remains of extinct birds and land snails, which are no longer present in Bermuda. This cave has also been known to contain fossil bats, reptiles, and land crabs. Scientists are now turning to caves all over the world to look for fossils of prehistoric flora and fauna. To date, the different types of fossils found in caves have included large land mammals, birds, bats, reptiles, plants, trees, pollen, and insects, all extinct and hundreds of thousands of years old. Ongoing studies of Blue Holes in the Bahamas are revealing several new species of plants and animals including a crocodile and land tortoise. These findings are bridging the evolutionary gaps between the past and present.


Question from: Jim
How can I get data on the exact location of the water line in the caves over time?

Answer from: Tom Iliffe, Director, Marine Biospeleology Lab, Texas A&M University
We are collecting submerged stalagmites from known depths in underwater caves which can be age dated using thorium-uranium ratios. Since stalagmites only form in air by dripping water, we know that sea level was below that point. Sometimes crystal knobs appear on stalactites precisely at sea level. Dating these knobs can tell us where sea level was at a specific time. Cave sediments also contain datable records of sea level. On our current project, we are looking for wave cut notches and drown reefs that provide a record of deep sea level events.


Question from: Jim
I got the idea that you are saying the ocean was ~5 degrees cooler 18,000 years ago. So, what does the data say knowing you can't directly measure oxygen isotopes in the ocean of 18,000 years ago? Is there any other way to estimate ocean temperatures of the old days?

Answer from: Tom Iliffe, Director, Marine Biospeleology Lab, Texas A&M University
There are a number of ways to measure paleo ocean temperatures and climate. In fact, you can measure oxygen isotopes from paleo oceans in several different ways. In order to measure paleo ocean temperatures, oxygen isotope ratios are obtained from several sources including foraminifera from ocean sediments, ice from ice cores in the Arctic and Antarctic, stalactites and stalagmites in caves, fossilized corals, and even tree rings. Just as sea surface temperatures vary with location and season, they have also varied with geological time periods. During the Ice Ages when the overall climate of the earth was significantly cooler and glaciers covered much of Canada and the Northern U.S., the temperature of the oceans were significantly cooler as well.


Question from: Jim
Do you know how far under water the cave floor that was dry ~18,000 years ago is now? It seems that some allowance should be made for the increased weight of water on the sea floor, too. The result could be that more water is needed to cause a rise in sea level due to more pressure depressing the sea bed. Maybe the sea level cannot change as much as believed because the sea floor flexes under an increased load.

Answer from: Tom Iliffe, Director, Marine Biospeleology Lab, Texas A&M University
During the last glacial maximum, about 18,000 years ago, sea level was 100 to 130 meters lower than today. There is direct evidence of this in the wave cut notches that we find along the sides of the Bermuda sea mount and from the presence of massive stalactites and stalagmites that only form in air by dripping water, deep in the depths of salt water caves in places like Bermuda, the Bahamas and Mexico. In addition, fossilized shallow water coral reefs have been found between 100 to 130 meters which supports sea level change as these reef ecosystems can only be formed in close proximity to the surface. The evidence found thus far proves that sea levels have been rising and falling significantly over hundreds of millions of years.


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