How the drama unfolded

A webcam captures the wall of mud and water in the Whangaehu Valley. Photo Supplied.

How the drama unfolded:

10.06am:

One of three DOC sensors at Crater Lake registers unusual earth vibrations.

10.42am:

The same sensor sounds another warning

10.50am:

The same sensor repeats another warning

11.00am: (Approximation)

The other two sensors at Crater Lake start sounding. The lahar is thought to began to occur at this point, over a period of about 45 minutes.

12.00pm:

Police announce closure of SH1 between Rangipo and Waiouru. SH49 between Waiouru and Ohakune is also closed. All rail services stopped at Waiouru and Ohakune.

12.45pm: (Approximation)

DOC sensors return to their normal background reading.

1.00pm (Approximation)

Whangaehu River levels peak just after 1.

3.55pm:

SH1 between Rangipo and Waiouru reopened.

4.29pm:

SH49 between Waiouru and Ohakune reopened

4.30pm:

Tangiwai rail bridge reopened subject to a 25 kph speed limit