Lake Powell cliff collapses on Memorial Day — VIDEO

Part of a large cliff fell into Lake Powell in southern Utah on Memorial Day, creating a temporary hazard for holiday boaters.

The collapse was reported by CNN, Fox 10 in Phoenix and other outlets through social media posts by boaters.

Officials with the Glen Canyon National Recreation Area, along the Arizona-Utah border, have not said what caused the collapse.

Lake Powell is the nation’s second-largest reservoir. It was created in the 1960s after the construction of Glen Canyon Dam along the Colorado River.

In March, the reservoir known as a boating mecca dipped below a critical threshold, raising new concerns about a source of power that millions of people in the U.S. West rely on for electricity.

Lake Powell’s fall to below 3,525 feet puts it at its lowest level since the lake filled after the federal government dammed the river. Lake Powell and its downstream counterpart, Lake Mead, are dropping faster than expected due to a megadrought.

About 5 million customers in seven states — Arizona, Colorado, Nebraska, Nevada, New Mexico, Utah and Wyoming — buy power generated at Glen Canyon Dam.

In Page, Arizona, which benefits from recreation at Lake Powell, officials launched a campaign in the spring to highlight that lower levels aren’t necessarily bad for visitors, noting receding shorelines have revealed sunken boats, canyons and other geographic wonders.

A shrinking Lake Mead has revealed boats and at least one body in a barrel.

— The Associated Press contributed to this report.