Cave stalactites and stalagmites. Credit: Santi Rodríguez / Adobe Stock

Ancient Cave Crystals Reveal Sea Levels Were 50 Feet Higher in Warmer Climate


Scientist studying ancient crystals in a Spanish cave have discovered disconcerting evidence that shows just how high sea levels can rise in a warmer climate.

4.4 million years ago, one of your ancestors measuring, about 4 feet (1.22 meters) tall, with a hairy body and snout-like face, known to science as Ardi, climbed trees with ease having a muscular body, long arms, wide-hands, and strong toes.

Ardipithecus ramidus is the earliest relation of anatomically-modern humans, Homo sapiens , and while she roamed her woodland habitat in East Africa , the surrounding shorelines were much higher than today, according to a new paper published on August 30 in  Nature.

The new research asks, “How much of earth’s biggest ice sheet melted during the Pliocene (5.33 million to 2.58 million years ago)?” and focuses on findings at the coastal Spanish limestone Artà Caves on the Balearic island of Mallorca. A study of 4.39 million-year-old “mineral bathtub rings”, properly called aragonite crystals and calcite deposits , formed in the cave’s ‘theater room’, have illustrated exactly how high the world’s seas and oceans got during the Pliocene Epoch , which scientists say was the hottest the earth is expected to get until 2100.

Artà Caves formations reveal ancient sea levels. (arvernho / Adobe Stock)

Artà Caves formations reveal ancient sea levels. ( arvernho / Adobe Stock)

When Ice Melts, Sea Levels Rise, It’s That Simple

The mineral deposits suggest that during the Pliocene Epoch seas were an alarming 52 feet (16 meters) higher on average than they are today. While this helps climate change scientists better understand what happened when ice sheets melted and ocean waters rose, it also rings alarm bells by hinting at how oceans could respond to climate change in the modern day.

Traditionally, paleoclimatologists reconstructed Pliocene sea level changes in two flawed ways.

The first method compared the ratios of isotopes (oxygen) in fossilized sea creatures against a global database of oxygen ratios and ice sheet cycles while the second method estimated historic sea levels based on the age of ancient coral reefs . The new analysis, called Artà, is different from all previous studies because it incorporates information about the subsequent rise and fall of the earth’s crust , which earlier studies had failed to account for.

Alan Haywood, a paleoclimatologist at Leeds University in England, spoke to reporters at Science News and said the new results suggest smaller ice sheets in Greenland and western Antarctica melted severely. Furthermore, only parts of the eastern Antarctic ice sheet melted during that era and that it remains unclear how today’s warming patterns will affect ice sheets. “Anything that gives us added information on how sensitive the ice sheets are … is going to be very important,” Haywood says.

Ancient Seas Were Much Higher Than Today

Mallorcan researchers first found the aragonite and calcite deposits on stalactites and stalagmites in the Artà Caves In the 1970s and established these phreatic overgrowths had accumulated over thousands of years, caused by seawater repeatedly lapping against the rocks, indicating changing tides. The new dating method was capable of reaching back much further in time and compared ratios of uranium to lead in the minerals to answer when exactly the much older Pliocene deposits formed.

Aragonite crystals locations and ages of such growths can help researchers track past sea levels. (Max Pixel / Public Domain)

Aragonite crystals locations and ages of such growths can help researchers track past sea levels. (Max Pixel / Public Domain )

In a nutshell, Dumitru’s team found that when the earth’s temperatures rose, it formed mineral deposits at heights measured from between 48 to 77 feet (15 to 24 meters) above today’s current sea level.

Pick Your Paper

These ancient stone features, in every conceivable sense, are ‘trees of life’ containing within their trunks, secrets of the ages. Beginning with one of the lower deposits at 48 feet (15 meters) the scientist ascertained that in the mid-Piacenzian Warm Period (3.3 million to 3 million years ago), global temperatures were 36 to 37 degrees Fahrenheit (2 to 3 degrees Celsius) warmer with sea levels 53 feet (16.2 meters) higher than today and that they “resemble leading forecasts for the year 2100”.

These ancient deposits from the Artà Caves provide data regarding temperatures and sea levels. (Cristian Bortes / CC BY-SA 2.0)

These ancient deposits from the Artà Caves provide data regarding temperatures and sea levels. (Cristian Bortes / CC BY-SA 2.0 )

That last finding just goes to show how quickly science moves, for only in 2009 a New Scientist article discussed two studies published in 2008 that suggested “sea-levels could rise  by approximately 4.3 feet (1.3 meters)  by 2100. The other  set the upper limit at 6.6 feet (2 meters) ”. Furthermore, these studies ‘proved’ the seas would take “a couple of thousand years to rise 82 feet (25 meters),” so it’s up to you to pick which paper to believe.

While the roots of the tree speak of impending oceanic Armageddon, as we move up toward the highest of the mineral deposits, they correspond with the Pliocene’s warmest period which is estimated to have been about 4.39 million years ago. The researchers calculated that at this time, temperatures were about 39 degrees Fahrenheit (4 degrees Celsius) higher than in pre-industrial times and that seas were about 77 feet (23.5 meters) higher than today.

Don’t Worry, We Will Be Fine

Now, this last part of the study focusing on events ‘4.39 million years ago’ is just after Ardi began swinging in trees about 4.4 million years ago. If a hairy, tree swinging, long-armed biped survived seas 77 feet (23.5 meters) higher than they are today, perhaps we will be just fine too. However, one should quickly recall that Ardi belonged to a species who did not build major population centers at sea level!

Top image: Cave stalactites and stalagmites. Credit: Santi Rodríguez / Adobe Stock

By Ashley Cowie

Next article