【推荐1】Check out our tsunami (海啸) facts and lean some interesting information related to these great walls of water that can cause so much destruction. Find out what causes tsunamis and read about some notable recent examples of tsunamis that have occurred around the globe.

Tsunamis are huge waves of water that are usually caused by earthquakes or volcanic eruptions.

As a tsunami approaches the shore, water may move back from the coast. If it is shallow enough, the water may be pulled back hundreds of meters. If you are in the area, observing this is a good indication that a tsunami is on the way.

Regions in tsunami danger zones often have warning systems in place to give people as much time to evacuate (撤离) as possible.

When tsunamis hit shallow water (often near the coast), they slow down but increase in height.

An earthquake in the Indian Ocean off Indonesia in December 2004 caused a tsunami that killed over 200, 000 people in 14 countries.

In March 2011, the Tohoku earthquake off the eastern coast of Japan caused a tsunami that was a major factor in the death of over 15, 000 people.

The tsunami waves created by the Tohoku earthquake reached heights of over 40 metres (131feet) in mine areas, wiping out coastal towns and causing a number of nuclear accidents.

The Japanese word “tsunami” literally means “harbour wave”.

Tsunamis are sometimes referred to as tidal waves but this term has fallen out of favour because tsunamis are not related to tides.

【推荐2】An earthquake is one of the most common natural disasters. It may cause great damage. So it is wise to learn some simple safety tips to protect yourself or your family members.

Fragile items, like those made of glass should usually be placed on a lower surface, near the ground instead of placing them on cupboards higher up. Never place them near your bed, sofas and other furniture where you would be sitting or lying down. When there is a strong movement, these pieces will fall on the floor directly and not on you.

There is a strong chance of short circuits (短路) and fire breakouts during an earthquake. Make sure you turn off electrical connections and gas immediately when an earthquake happens.

During an earthquake, lie beneath an object that is not easily damaged. Do not go near objects that could directly fall on you. Never use the elevator to go down. Stay inside until the shaking stops and it is safe to go outside. Research has shown that most injures happen when people inside buildings try to go out. Use the staircases at all times.

If you are outdoors, do not take shelter under a tree, streetlights, electric poles or tall buildings. If you are driving, stop your car and stay in a safe place. Do not park your car under a tree or any tall object.

If trapped in debris (瓦砾堆), cover your mouth with a handkerchief or clothing. Tap on a pipe or wall so rescuers can find you. Use a whistle (哨子) if it is available. Never shout for help. Shouting can cause you to breathe in dangerous amounts of dust. Do not light a match because you may burn yourself. Do not move about or kick up dust.

【推荐3】California has lost half its big trees since the 1930s, according to a study to be published Tuesday and climate change seems to be a major factor（因素）.

The number of trees larger than two feet across has declined by 50 percent on more than 46, 000 square miles of California forests, the new study finds. No area was spared or unaffected, from the foggy northern coast to the Sierra Nevada Mountains to the San Gabriels above Los Angeles. In the Sierra high country, the number of big trees has fallen by more than 55 percent; in parts of southern California the decline was nearly 75 percent.

Many factors contributed to the decline, said Patrick Mclntyre, an ecologist who was the lead author of the study. Woodcutters targeted big trees. Housing development pushed into the woods. Aggressive wildfire control has left California forests crowded with small trees that compete with big trees for resources（资源）.

But in comparing a study of California forests done in the 1920s and 1930s with another one between 2001 and 2010, Mclntyre and his colleagues documented a widespread death of big trees that was evident even in wildlands protected from woodcutting or development.

The loss of big trees was greatest in areas where trees had suffered the greatest water shortage. The researchers figured out water stress with a computer model that calculated how much water trees were getting in comparison with how much they needed, taking into account such things as rainfall, air temperature, dampness of soil, and the timing of snowmelt（融雪）.

Since the 1930s, Mclntyre said, the biggest factors driving up water stress in the state have been rising temperatures, which cause trees to lose more water to the air, and earlier snowmelt, which reduces the water supply available to trees during the dry season.