The deepest part of the Indian Ocean is one of the least explored spots on Earth. It’s also one of the most dangerous. Major earthquakes have rocked it, causing major destruction—including what may be the deadliest natural disaster of the 21st century.

The Sunda Trench—also known as the Java Trench—is a gash in the ocean floor. It curves around the islands of Sumatra and Java, on the eastern edge of the Indian Ocean, between Australia and India. It’s about 2,000 miles long, and up to four and a half miles deep.

Only one expedition has studied the trench in detail. In 2019, both people and robotic vehicles descended to its floor. They found an abundance of life, including several new species. One highlight was a possible sea squirt—a critter that looked like a wrinkled balloon tied to a long string.

The Sunda Trench was created by the motions of the plates that make up Earth’s crust. Plates to the west are plunging below the plates to the east. The zone where they intersect forms a V-shaped hollow.

It’s an active zone—the motions of the plates trigger powerful earthquakes. A quake in 2004 caused a tsunami that killed a quarter of a million people around the Indian Ocean. In this century, only an earthquake in Haiti might have been deadlier. The event led to the creation of a tsunami warning system for the region—keeping a lookout for danger from the Sunda Trench.

Seaweed farms offer many benefits. They provide food for people, habitat for fish and other organisms, and protection against erosion during storms. They can help prevent “red tides,” and could become a source of biofuel.

Seaweed stores carbon in the sediments on the ocean floor. That helps reduce the amount of carbon dioxide in the atmosphere, which is the major cause of our warming climate.

Wild seaweed forests already stash away huge amounts of carbon. Farms cover a much smaller area, so their benefit is smaller. But seaweed farming is a “growing” business—the yield has been increasing by more than seven percent per year. Almost all of the farming takes place in Asia. The United States is a minor player, but farms have been developed in New England, the Pacific Northwest, and Alaska.

Researchers studied the sediments below 20 seaweed farms in various parts of the world. The oldest, in Tokyo Bay, has been around for 320 years. The largest, in China, covers 58 square miles.

The scientists found that the amount of carbon in the sediments below the farms was twice that found in the surrounding sediments. And they found that as a farm ages, it becomes more efficient at “planting” the carbon.

Estimates say that seaweed farms could cover many times their present area by 2050. And the researchers said that if the farms are efficiently managed, they could become important weapons in the fight against our warming climate.

Alexandria, Egypt, has stood for almost 2400 years. Today, though, parts of it are crumbling—one building at a time. As Earth’s climate changes, the Mediterranean Sea is rising, the coast is eroding, and saltwater is seeping into groundwater supplies. That weakens buildings, causing them to collapse. And according to a recent study, without action to protect the coastline, the problem will get worse in the years ahead.

Alexandria is the largest city on the Mediterranean, and one of the busiest ports. But its maritime location is causing trouble. Researchers looked at records of building collapses over the past quarter century. They also compared the coastline to that of previous decades, studied the soil, and made other observations.

They found that 280 buildings have collapsed in the past 20 years. Over that span, the rate of collapse jumped from fewer than one per year to almost 40. Almost all of the destroyed buildings were within a mile of the coast.

The jump was largely the result of climate change. Higher sea level and stronger storms have eroded the coastline by an average of 12 feet per year, with one district averaging 120 feet. And seawater is filtering into aquifers below the city. That corrodes foundations, causing buildings to crumble.

The scientists recommended creating dunes and greenbelts along the coast to keep the Mediterranean at bay—and keep Alexandria from crumbling into the sea.