1964 Alaskan earthquake

The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, occurred at 5:36 P.M. AST on Good Friday, March 27.Across south-central Alaska, ground fissures, collapsing structures, and tsunamis resulting from the earthquake caused about 139 deaths.

Lasting four minutes and thirty-eight seconds, the magnitude 9.3 megathrust earthquake was the most powerful recorded in U.S. and North American history. Soil liquefaction, fissures, landslides, and other ground failures caused major structural damage in several communities and much damage to property. Anchorage sustained great destruction or damage to many inadequately earthquake engineered houses, buildings, and infrastructure (paved streets, sidewalks, water and sewer mains, electrical systems, and other man-made equipment), particularly in the several landslide zones along Knik Arm. Two hundred miles southwest, some areas near Kodiak were permanently raised by 30 feet (9.1 m). Southeast of Anchorage, areas around the head of Turnagain Arm near Girdwood and Portage dropped as much as 8 feet (2.4 m), requiring reconstruction and fill to raise the Seward Highway above the new high tide mark.

In Prince William Sound, Port Valdez suffered a massive underwater landslide, resulting in the deaths of 30 people between the collapse of the Valdez city harbor and docks, and inside the ship that was docked there at the time. Nearby, a 27-foot (8.2 m) tsunami destroyed the village of Chenega, killing 23 of the 68 people who lived there; survivors out-ran the wave, climbing to high ground. Post-quake tsunamis severely affected Whittier, Seward, Kodiak, and other Alaskan communities, as well as people and property in British Columbia, Washington, Oregon, and California. Tsunamis also caused damage in Hawaii and Japan. Evidence of motion directly related to the earthquake was reported from all over the earth.

As a result of the earthquake, 139 people are believed to have died: Fifteen died as a result of the earthquake itself, 106 died from the subsequent tsunami in Alaska, 5 died from the tsunami in Oregon, and 13 died from the tsunami in California. The quake was a reported XI on the modified Mercalli Intensity scale "indicating major structural damage, and ground fissures and failures".Property damage was estimated at about $311 million($2.28 billion in current U.S. dollars).

1991 Mt. Pinatubo Volcano Eruption

Mount Pinatubo  is an active stratovolcano in the Cabusilan Mountains on the island of Luzon, near the tripoint of the Philippine provinces of Zambales, Tarlac, and Pampanga. Before the volcanic activities of 1991, its eruptive history was unknown to most people. It was heavily eroded, inconspicuous and obscured from view. It was covered with dense forest which supported a population of several thousand indigenous people, the Aetas, who fled to the mountains during the Spanish conquest of the Philippines.

The volcano's Plinian / Ultra-Plinian eruption on 15 June 1991 produced the second largest terrestrial eruption of the 20th century after the 1912 eruption of Novarupta in the Alaska Peninsula. Complicating the eruption was the arrival of Typhoon Yunya (Diding), bringing a lethal mix of ash and rain to areas surrounding the volcano. Successful predictions at the onset of the climactic eruption led to the evacuation of tens of thousands of people from the surrounding areas, saving many lives, but the surrounding areas were severely damaged by pyroclastic flows, ash deposits, and subsequently, by the lahars caused by rainwaters re-mobilizing earlier volcanic deposits causing extensive destruction to infrastructure and changing the river systems months to years after the eruption.

The effects of the eruption were felt worldwide. It ejected roughly 10,000,000,000 tonnes (1.1×1010 short tons) or 10 km3(2.4 cu mi) of magma, and 20,000,000 tonnes (22,000,000 short tons) SO

2, bringing vast quantities of minerals and metals to the surface environment. It injected more particulate into the stratosphere than any eruption since Krakatoa in 1883. Over the following months, the aerosols formed a global layer of sulfuric acid haze. Global temperatures dropped by about 0.5 °C (0.9 °F) in the years 1991-93 and ozone depletion temporarily increased substantially.

A reported 847 people were killed by the eruption, mostly by roofs collapsing under the weight of accumulated wet ash, a hazard amplified by the simultaneous arrival of Typhoon Yunya. The evacuation in the days before the eruption certainly saved tens of thousands of lives, and has been hailed as a great success for volcanology and eruption prediction. However, damage to healthcare facilities and the spread of illnesses in relocation facilities due to poor sanitation led to rising death tolls in the months after the eruption.

After the eruption, about 500,000 people continue to live within 40 km (25 mi) of the mountain, with population centers including the 150,000 in Angeles City and 30,000 at Clark Freeport Zone.