Title: Mount Ruapehu
Content:  Ruapehu saw a period of heightened activity between 1966 and 1982, with multiple small eruptions occurring in Crater Lake and two larger eruptions in 1969 and 1975, which ejected rocks across the summit region and produced significant lahars. The eruption in 1969 occurred in the early hours of 22 June. It was a moderate phreatic eruption, which blasted rocks up to 1 km northwest of the crater and sent lahars down several valleys. The Whakapapa skifield was left covered in mud. This was the largest eruption since 1945. A larger phreatic eruption occurred at 3:59 a.m. on 24 April 1975, blasting rocks up to 1.6 km northwest of the crater, against the wind, and depositing ash more than 100 km to the southeast. Nine minutes of seismic activity preceded the eruption, but crater dilation had been measured 
Title: Mount Ruapehu
Content:  Ruapehu erupted at 10:24 p.m. on 4 October 2006. The small eruption was marked by a magnitude 2.9 volcanic earthquake and sent waves 4–5 m tall crashing into the wall of the crater. No ash was erupted into the atmosphere, and the eruption is presumed to have occurred entirely underwater. At 11:22 a.m. 18 March 2007, the tephra dam which had been holding back Crater Lake burst, sending a lahar down the mountain. An estimated 1.9–3.8 million cubic metres of mud, rock, and water travelled down the Whangaehu river. ERLAWS activated, sending an alarm to pagers at 11:25 a.m. and automatically activating warning lights and barrier arms to close roads and 
Title: Mount Ruapehu
Content:  Only one eruptive event has been recorded at Ruapehu since the 2007 eruption—a minor event on 13 July 2009 when a small volcanic earthquake beneath Crater Lake caused the lake water level to rise 15 cm and triggered a snow slurry lahar in the upper Whangaehu valley. Since then, Crater Lake has continued its regular cycle of heating and increased gas emissions, although with periods of sustained high temperatures that occurred in 2011, 2016 and 2019. Eruptions at Ruapehu are expected to continue much as they have for the past 2,000 years, with frequent minor eruptions and more significant events every 20–30 years, although the possibility of larger events like the Pahoka-Mangamate event cannot be ruled out. Minor eruptions such as the one in 2007 can occur at any time without warning, but in historic times, major eruptions such as the ones in 1995–96 have only 
Title: Mount Ruapehu
Content:  Lava flows that have been erupted from Ruapehu since the last glacial maximum are called the Whakapapa Formation. These flows all erupted between 15,000 and 2,000 years ago from a number of different craters on the summit of Ruapehu as well as from craters on the northern and southern flanks of the mountain. Approximately 10,000 years ago, a series of major eruptions occurred, not just on Ruapehu, but also at the Tama Lakes between Ruapehu and Tongariro volcanoes. This period of intense eruptions is called the Pahoka-Mangamate event and is thought to have lasted between 200 and 400 years. On Ruapehu, lava was erupted from Saddle Cone—a flank crater on the northern slopes—and from another crater on the southern slopes. This southern crater erupted three times, and lava flows from this crater traveled nearly 14 km to the south. There is evidence that a sector collapse on 
Title: Mount Ruapehu
Content:  water under the lake. The first significant eruption took place at 8:05 a.m. on 18 September 1995, raining tephra onto the summit region and sending lahars down the mountain. On 23 September, an even larger eruption blasted rocks up to 1.5 km from the crater, sent lahars down three valleys, and generated an eruption column 12 km high. Phreatomagmatic eruptions occurred through the rest of the month and throughout October, with some eruptions continuing for hours at a time. Ash fell up to 250 km downwind. Explosive eruptions on 11 October emptied Crater Lake of water. Following this, activity died off until 15 June 1996 when 
Title: Mount Ruapehu
Content:  northwestern slopes about 9,400 years ago formed the amphitheatre that now comprises the Whakapapa skifield and left an extensive avalanche deposit on the northwestern ring plain that can still be seen today. Eruptions between 10,000 and 2,500 years ago generated lava flows that all flowed into this amphitheatre and created the slopes of the modern skifield. For the past 2,000 years, activity at Ruapehu has been largely focused through a crater lake at the summit. Eruptive activity has typically consisted of relatively small but explosive phreatomagmatic eruptions occurring every few decades and lasting several months each. In recorded history, these eruptions have occurred about 50 years apart, in 1895, 1945 and 1995–1996. Minor phreatic or hydrothermal eruptions occur every few years on average, with notable minor eruptions occurring in 1969, 1975, and 2007. More than 600 eruptive events of various sizes have been documented since 1830.
Title: Mount Ruapehu
Content:  Ruapehu entered an eruptive phase in March 1945 after several weeks of volcanic tremors. The first indication of an eruption was reported on 8 March, with ashfall seen on the eastern slopes. A lava dome was observed in Crater Lake on 19 March but was destroyed in a series of explosive eruptions over the following week. A second, larger lava dome appeared in May, which continued to grow over the following months and had emptied Crater Lake of water by July. Eruptions increased from August through November. A particularly powerful eruption in the early hours of 21 August was heard in Hawkes Bay and the Tararua District, loud enough to awaken people from sleep and cause alarm. Eruptions began declining in December and had ended by January. The eruptions dispersed ash across most of the 
Title: Mount Ruapehu
Content:  emission of volcanic gases, indicating that the vents under Crater Lake are open to gas escape. Evidence suggests that an open-vent system such as this has been in place throughout Ruapehu's 250,000 year history. This prevents build-up of pressure and results in relatively small, frequent eruptions (every 20–30 years on average) at Ruapehu compared to other andesitic volcanoes around the world. Crater Lake is emptied by major eruptions, such as the ones in 1945 and 1995–1996, but refills after eruptions subside, fed by melting snow and vented steam. In historic times, major eruptions have deposited a tephra dam across the lake's outlet, preventing lake overflow into the Whangaehu valley. The dam collapses after several years 
Title: Mount Ruapehu
Content:  limestone. It has not been clearly established when Ruapehu first began erupting, only that eruptions began at least 250,000 years ago and possibly as early as 340,000 years ago. Ruapehu has been built in four distinct stages of relatively intense eruptive activity followed by periods of relative quiet. Each of these four stages of activity has left behind distinct rock formations, named the Te Herenga Formation (erupted 250,000–180,000 years ago), the Wahianoa Formation (erupted 160,000–115,000 years ago), the Mangawhero Formation (erupted 55,000–15,000 years ago), and the Whakapapa Formation (erupted 15,000–2,000 years ago). Each of these rock formations is composed of lava flows and tuff breccias, and studies of these formations has revealed how volcanic activity at 
Title: Mount Ruapehu
Content:  trains. There was no serious damage and no injuries. A toilet block at the Tangiwai memorial was destroyed, but the memorial had already been closed due to the lahar threat. One family was trapped for around 24 hours after the lahar swept away the access route to their home. At 8:16 p.m. on 25 September 2007, volcanic tremor was detected underneath Ruapehu, which was followed at 8:26 p.m. by an explosive surtseyan eruption. The explosive phase of the eruption lasted for less than a minute and blasted ash, mud, and rocks northward, reaching to about 2 km from Crater Lake. Two climbers were caught in the eruption at Dome Shelter, an 

Question: when was the last time mount ruapehu erupted?
Answer: 25 September 2007.