Learn German: Wir beobachten den Ausbruch immer, selbst wenn der Vulkan nachts ausbricht. - We always observe the eruption, even if the volcano erupts at night.

The phrase selbst wenn (even if) acts as a subordinating conjunction. This means it introduces a subordinate clause and kicks the conjugated verb of that clause, ausbricht, to the very end of the sentence.

Why is ausbricht written as a single word here instead of being separated?

The verb is ausbrechen (to erupt), which is a separable verb. In a normal main clause, it would split, as in der Vulkan bricht aus. However, because selbst wenn pushes the verb to the end of the subordinate clause, the prefix aus and the conjugated verb bricht must reunite into the single word ausbricht.

What would the word order be if we started the sentence with the selbst wenn clause?

If you put the subordinate clause first, that entire clause acts as the first block of information for the sentence. The main clause must then immediately start with its verb to keep the core verb in the second position. It would become: Selbst wenn der Vulkan nachts ausbricht, beobachten wir den Ausbruch immer.

Why does nachts have an s at the end?