Malta’s Landscape of Limestone

Today’s tale is the respond to to the December 2022 puzzler.

Malta, the archipelago located in between the Italian island of Sicily and the North African coast, grew from elements that had been after at the base of the sea. Thousands and thousands of yrs afterwards, these elements would variety the bedrock of the region’s created setting.

The Operational Land Imager-2 (OLI-2) on Landsat 9 obtained these natural-colour photos of the archipelago on Oct 27, 2022. Most popular in the impression earlier mentioned are the island nation’s three greatest islands: Malta, Gozo, and Comino.

Detect the yellow-grey hue throughout a lot of the islands, specifically at constructed-up places and beaches. This is the coloration of limestone—a big geologic element of the island and a broadly applied developing substance. The oldest rocks are lower coralline limestone, which shaped as the skeletons of coral and other aquatic creatures constructed up from at the seafloor starting up close to 30 million a long time in the past. The second-oldest rocks are globigerina limestone, which shaped from the calcium carbonate shells of marine plankton. Outcrops of these rocks span about 70 p.c of the islands.

In Valletta, the island nation’s money town, fortifications had been designed applying limestone excavated from encompassing ditches. The walled city—built following the Siege of Malta in 1565—is situated on a peninsula in between two harbors, which has helped the perimeter of this UNESCO earth heritage web-site to stay generally unchanged.

There are locations in which use of the islands’ limestone for constructing dates even farther back. Numerous megalithic temples throughout the islands had been crafted throughout the fourth and third millennium B.C.E. and are between the oldest-identified freestanding constructions on Earth. Island inhabitants normally utilised the tougher coralline limestone for exterior walls and the softer globigerina limestone for inside areas and decoration.

While the structures have stood for millennia, they remain susceptible to degradation from the surrounding setting. The thorough graphic displays the area all over the prehistoric complex of Tarxien. Notice the white tent, which was erected about the advanced to help shelter it from the weathering effects of rain and daylight. Experts go on to keep an eye on how these and other things, these kinds of as salt, humidity, and temperature fluctuations, have an effect on the buildings.

NASA Earth Observatory photos by Joshua Stevens, using Landsat facts from the U.S. Geological Study. Tale by Kathryn Hansen.