In this image, you can see the volcanic plume extending into the sky. But you can also see the atmospheric shock wave from the eruption, which pushed the clouds back into a ring in the sky. Also visible is a smooth, fluffy white cloud on top of the rapidly rising ash column. This is likely a result of rapidly rising water vapor condensing on top of the plume.
A detail of the image also reveals what is known as the pyroclastic flow. This is a mixture of super hot gas and ash that can travel at up to 130 miles per hour. It's similar to the kind of rapidly moving pyroclastic surge that supposedly wiped out Pompeii so quickly, killing everyone in its path. It's a beautiful image, dense with interesting quirks that demonstrate just how powerful, dangerous and complex volcanoes are.