Every car was checked, but not every resident was allowed into the town because the crowd was so large. There was a long traffic jam with a wait of several hours. In Grindavík itself, each household was only given five minutes to complete tasks.
However, on Tuesday afternoon when they arrived, there was another new alarm and the area had to be completely evacuated once again. The reason for this was a high level of sulphur dioxide in the air, caused by volcanic gases.
Earthquakes caused by the rupture of rock layers
In recent weeks there have been thousands of earthquakes in the area. The tremors are caused by the movement of magma, which has been collecting in a kind of storage chamber at a depth of four to five kilometres for about two and a half weeks.
In an active volcano, the magma rises to the surface, sometimes releasing as just ash and smoke. A lack of magma supply means a volcano is extinct.
To make more room, magma pushes itself through cracks and crevices in the rock, which repeatedly breaks open. This breaking up of the rock layers can be felt as an earthquake.
If the magma reaches the earth's surface somewhere during these processes, the volcanic eruption begins. However, it is difficult to specify the exact time period that this may happen.
The exact location can also only be roughly estimated. The magma on Iceland is currently around 500 metres below the earth's surface.
Magma channel directly beneath Grindavík
The magma channel currently runs directly beneath the town of Grindavík and is around 15 km long. It is also possible that the magma will initially move sideways towards the coast and that the eruption could even take place under the sea.