At 8:32 a.m. local time the next day (18 May), an earthquake measuring magnitude 5.1 rocked the area, triggering the landslide that started the main eruption. In a matter of seconds, vibrations from the earthquake loosened of rock on the mountain's north face and summit, creating a massive landslide. With the loss of the confining pressure of the overlying rock, Mount St. Helens began to rapidly emit steam and other volcanic gases. A few seconds later, it erupted laterally, sending swift pyroclastic flows down its flanks at near supersonic speeds. These flows were later joined by lahars. Before being struck by a series of flows that, at their fastest, would have taken less than a minute to reach his position, Johnston managed to radio his USGS co-workers with the message: "Vancouver! Vancouver! This is it!" Seconds later, the signal from the radio went silent, and all contact with the geologist was lost. Initially, there was some debate as to whether Johnston had survived; records soon showed a radio message from fellow eruption victim and amateur radio operator Gerry Martin, located near the Coldwater peak and farther north of Johnston's position, reporting his sighting of the eruption enveloping the Coldwater II observation post. As the blast overwhelmed Johnston's post, Martin declared solemnly that the camp and car sitting to his south were covered: "It's gonna get me, too," he said before his radio went silent.