AMECAMECA, Mexico — Glaciers that crown a Mexican volcano could disappear by 2015 with scientists pointing to global warming as a chief cause of their demise.

Until recently, the glacial field on Iztaccihuatl, a dormant volcano and one of two white-capped peaks that can be seen from Mexico City, was expected to be gone within a few decades.

But studies show rising world temperatures are melting the glaciers faster than previously thought, said Hugo Delgado, a glaciologist at Mexico City’s UNAM university who thinks the massive blocks of ice will be gone within four years.

“What we’ve seen at Iztaccihuatl is an intense period of glacial retreat in the last few years, which has changed the picture,” Delgado said.

NUEVO LAREDO, Mexico – Mexican authorities opened shelters and warned people to watch out for mudslides Monday as Tropical Storm Hermine approached the northeastern border with Texas, the second major storm to hit the area this season.

Hermine could approach hurricane strength before making landfall early Tuesday in a sparsely populated area about 50 miles (80 kilometers) south of Matamoros, a city bordering Brownsville, Texas, according to the National Hurricane Center in Miami.

A hurricane watch was issued for the area from Rio San Fernando, Mexico, northward to Baffin Bay in Texas.