An earthquake hit Gansu just before midnight on Dec 18, 2023. Besides bringing down buildings, the earthquake caused a sand boil (砂涌) in two villages in neighboring Qinghai Province. The mud (泥) was about 2 to 3 meters deep on average, covering nearly 60,000 square meters.

A sand boil happens when the space between sand particles (颗粒) is completely filled with water.

Everyone tries to get to school on time. But when bad weather gives you trouble, can you still make it before the bell rings?

In northern China during spring, big sandstorms (沙尘暴) often make trouble for students and everyone else. When the sky is dark with sand (沙子), buses and cars all move much more slowly. Sometimes, people can’t even see for 20 meters. Sandstorms usually happen in spring. They have happened in more than 10 provinces in northern China this year.

People in southern China don’t have to worry about this kind of bad weather. Most of the sand comes from Gansu and Inner Mongolia (内蒙古). In northern China, lots of places have few trees and don’t get much rain. People there have been cutting down too many trees. When there aren’t many trees, the ground can’t keep enough water. Over the years, the ground dries up and turns to sand. When spring comes and the ice melts (融化), the ground becomes looser (更松散的). Strong winds take the loose sand into the sky.

Sandstorms are bad for people’s health. If people breathe too much sand, they could cough or have asthma (哮喘). Sandstorms also give farmers lots of problems. Sometimes their sheep get lost in the storms and never get back home. The winds also tear down farmers’ houses.

To stop sandstorms, you can ask your parents to help you plant some trees this spring. If you see people cutting down too many trees, tell them about the dangers of sandstorms, and ask your government to stop them from cutting.

California is burning! Wildfires have spread across the US state since Oct. 23, 2019 and smoke has filled its skies.

Take the Kincade Fire in northern California for example. It forced 200,000 people to leave their homes within one week. The state's largest power company cut power to about 206,000 homes in order to stop more fires from breaking out, CBS News reported.

California has seen many wildfires in recent years. Nine of the 10 biggest fires have happened since 2000, including five since 2010, according to The New York Times.

Why is this? California has the perfect wildfire conditions, Park Williams, a US climate expert (专家),told The New York Times. It has dry air and high temperatures from spring through late fall. At the same time, seasonal winds blow across the state every year, causing the wildfires to spread quickly and last for weeks.

Global (全球的) warming has also made the fires worse in recent years .It has dried out the state's trees and other plant life, causing them to burn more easily.

Humans have played a role as well. Burning campfires ,garbage debris (垃圾碎片), and cigarette butts (烟头) can easily cause wildfires.

Humans have caused 90 percent of California's wildfires, according to the US National Park Service.