Man, it’s a hot one. The scientist recently interviewed about the current state of the Hawaii Kilauea Volcano eruption didn’t quote Rob Thomas directly, but she might as well have. The lava flowing from the volcano, now in its fourth week of intense eruption, is at its hottest temperature yet — and this might be as hot as it gets.

What does it mean for a thing to be as hot as possible? Earth’s geology allows us to avoid contemplating the infinite. On this planet, the hottest temperatures exist at the core, which is thought to be as hot as the surface of the sun. But stuff from the core doesn’t bubble up to the surface; molten rock from the mantle, however, does. And, as U.S. Geological Survey scientist Wendy Stovall told reporters in a press conference on Thursday, that’s how hot the lava is right now.

“This is the hottest lava that we’ve seen in this eruption, even just a matter of 50 degrees centigrade makes a big difference in how quickly lava flows can move and how they behave once the magma exits the vent,” Stovall said.

“It can’t get hotter than where we are. We are pretty much tapping mantle temperatures right now.”

The mantle is the extremely thick layer of melty rock underneath the Earth’s crust. At roughly 1,800 miles (2,900 kilometers) thick, the mantle is a bubbling hellscape of semi-solid rock with a texture not unlike Silly Putty®, as the USGS puts it. It’s super thick because it contains a lot of iron, magnesium, and calcium than the crust. And because the pressure is so great in the mantle, buckling under the weight of our world, the temperature skyrockets to mind-searing heights: In 2017, scientists reported that the mantle can reach temperatures of up to 2,570° F (1,410 °C).

earth mantle core
The Earth's mantle, in orange, is hot -- but not as hot as the core.

Stovall’s statement suggests that the temperature of the lava, which is now much more fluid as a result of all that heat, has now reached this unfathomable peak, though she did not give an exact temperature. Scientists usually use the color of the lava as a rough indicator of how hot it is, with red being “cool” (about 1,472 °F), orange being slightly warmer (about 1,472–1,832 °F), and yellow being the hottest (from 1,832–2,192 °F), according to the USGS.

In the past, Kilauea’s lava has reached temperatures of at least 2,140 ° F. Now, as aerial photographs show, the lava pouring out of Kilauea is a striking yellow, suggesting it’s as hot as it can get.