La Serena, CHILE (CBS News) — Tens of thousands of tourists flocked to cities and towns across northern Chile and Argentina to stake out spots in one of the world’s best locations to witness Tuesday’s total solar eclipse. A solar eclipse occurs when the moon passes between the Earth and the sun and scores a bull’s-eye by completely blocking out the sunlight.

Millions were expected to gaze at the cosmic spectacle that will begin at 10:24 a.m. local time (11:24 p.m. PT) in the South Pacific and sweep along a path 6,800 miles across open waters to Chile and Argentina. Those are the only places where the total eclipse will be seen, aside from an uninhabited island out in the Pacific.

The eclipse is expected to make its first landfall in Chile at 3:22 p.m. (12:22 p.m. PT) in La Serena, a city of some 200,000 people where the arrival of more than 300,000 visitors forced the local water company to increase output and service gas stations to store extra fuel. Police and health services were also reinforced.