was observed on the south side. Worried that the amount of pressure on the magma underground was increasing, scientists analyzed gases by the crater, and found high traces of sulfur dioxide. After this discovery, they began to regularly check the fumarolic activity and monitor the volcano for dramatic changes, but none were observed. Disheartened, they instead opted to study the growing bulge and the threat an avalanche could have for humans relatively near the volcano. An evaluation of the threat was carried out, concluding that a landslide or avalanche in the Toutle River could spawn lahars, or mudflows, downstream. At that point, the previously consistent phreatic activity had become intermittent. Between May 10 and 17, the only change occurred on the volcano's north flank, as the bulge increased in size. On May 16 and 17, the mountain stopped its phreatic eruptions completely. The active Mount St. Helens was radically different from its dormant form, now featuring an enormous bulge and several craters. In the week preceding the eruption, cracks formed in the north sector of the volcano's summit, indicating a movement of magma. At 8:32 a.m. local time the next day (May 18), 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: "Gentlemen, the camper and car that’s