Surface flows of smooth pahoehoe lava from Kilauea Volcano continued to pro­gress Sunday across the pali and upper coastal plain of the abandoned Royal Gardens subdivision.

A series of deflation and inflation cycles over the past week has elevated a lava lake within Kilauea Volcano’s Halemaumau Overlook vent, resulting in a nightly glow visible from the Jaggar Museum on Crater Rim Drive, according to the U.S. Geological Survey’s Hawaiian Volcano Observatory.

Deflation-inflation cycles — referred to as "DI events" — are marked by sudden deflation or sinking of the ground that lasts between one and three days, followed by equally sudden inflation that returns the slope to previous levels. They are measured by instruments called tiltmeters.

The actual amount of caving during deflation is only about an inch and appears to be caused by pressure changes about a half-mile beneath the eastern margin of the crater, according to the observatory.

The observatory reported that DI events are recorded both at Kilauea’s summit and at Puu Oo in the east rift zone, originating at the summit and echoing hours later at Puu Oo.

The number of DI events recorded at the volcano has risen sharply since the start of Kilauea’s summit eruption in 2008, from five to 10 per year before 2008 to 87 in 2011. There have been 37 such events so far this year.

The observatory explains that when magma loses gas, it becomes dense and sinks, allowing less dense, gas-rich magma to rise.

"DI events might be an expression of convection, with the deflation phase corresponding to sinking of dense magma, and inflation resulting from the rise of gas-rich magma," said U.S. Geological Survey scientist Jim Kau­ahi­kaua in his Friday "Volcano Watch" report.

According to Kauahikaua, frequent DI events can disrupt lava flows from the east rift zone, while periods of no DI events can allow lava from Puu Oo to develop tube systems to the ocean.