Deserts are found where there is little rainfall or where rain for a whole year falls in only a few weeks' time. Ten inches of rain may be enough for many plants to survive if the rain is spread throughout the year. If it falls within one or two months and the rest of the year is dry, those plants may die and a desert may form.

    Sand begins as tiny pieces of rock that get smaller and smaller as wind and weather wear them down. Sand dunes (沙丘) are formed as winds move the sand across the desert. Bit by bit, the dunes grow over the years, always moving with the winds and changing the shape. Most of them are only a few feet tall, but they can grow to be several hundred feet high.

There is, however, much more to a desert than sand. In the deserts of the southwestern United States, cliffs (悬崖) and deep valleys were formed from thick mud that once lay under a sea more than millions of years ago. Over the centuries, the water dried up. Wind, sand, rain, heat and cold all wore away at the remaining rocks. The faces of the desert mountains are always changing –-very, very slowly —as these forces of nature continue to work on the rock.

    Most deserts have a surprising variety of life. There are plants, animals and insects that have adapted to life in the desert. During the heat of the day a visitor may see very few signs of living things, but as the air begins to cool in the evening, the desert comes to life. As the sun begins to rise again in the sky, the desert once again becomes quiet and lonely.

    How can we reduce the risk?

    There are four general approaches to dealing with volcanic dangers. We can try to keep the danger from occurring—often an impossible task. We can try to change its path or reduce its impact on existing development. We can take steps to protect future development. We can also do our best to have disaster response plans in place before they are needed.

    Removing the Threat

    Clearly, there is no way to stop an eruption. We can, however, attempt to reduce the eruption's effects by strengthening structures, for example, building protective works such as walls to make lava (熔岩) flow away from developed areas. Such efforts can be and have been successful, but are of limited use in a large-scale eruption.

    Planning for the Future

    Protecting future development from volcanic dangers is a simple task. Before building houses, we should judge the risk. If the risk seems too great, a safer location should be found. This type of planning is very effective, but all too often, people are drawn to the lush(葱郁的)，rolling land of a quiet volcano.

     Disaster Preparedness (预案)

    When a volcano comes to life, a few weeks may not be enough time to avoid a tragedy. Planning is the key to saving lives. Well before the warning signs occur, people must be educated about volcanic dangers. Escape plans must be in place. Communication between scientists, officials, the media, and the general public should be practiced. Emergency measures must be thought out and agreed upon.

    If you doubt the importance of these efforts, take another look at past volcanic tragedies, such as the eruption of Nevado del Ruiz. Communication failures left the town of Armero unprepared for escape. When a deadly mudflow came down the slope (斜坡), 21,000 people—90 percent of the town's people—died.

    Two things changed my life: my mother and a white, plastic, daisy bike basket. I would be a different person if my mom hadn't turned a silly bicycle accessory(配件) into a life lesson I carry with me today.

    It was summer and, one day, my mother drove me to the bike shop to get a tire fixed — and there it was in the window. White, shiny, plastic and decorated with daisies, the basket seemed so appealing and I knew I had to have it.

    "Mom, please can I get it? I'll do extra chores for as long as you say. I'll do anything, but I need that basket. I love that basket. Please, Mom. Please?"

    "You know," she said, gently rubbing my back while we both stared at what I believed was the coolest thing ever, "If you save up, you could buy this yourself."

    "By the time I make enough it'll be gone!"

    "Maybe Roger here could hold it for you," she smiled at Roger, the bike guy.

    "For that long? He can't hold it for that long, Mom. Someone else will buy it. Please, Mom, please?"

    "There might be another choice," she said. My mother bought the beautiful basket and put it safely out of reach in some hiding place I couldn't find. Each week I eagerly counted my growing nest egg earned by extra work here and there (washing the car, helping my mother make dinner, delivering milk around the neighborhood). And then, weeks later maybe, I counted, re-counted and jumped for joy. Oh, I made it! I finally had the exact amount we'd agreed upon.

    Days later, the unthinkable happened. A neighborhood girl I'd played with appeared with the exact same basket fixed to her shiny, new bike. I rode my bike fast home to tell my mother about this disaster, this horrible turn of events.

    And then came the lesson I've taken with me through my life: "Honey, your basket is extra-special," Mom said, gently wiping away my hot tears. "Your basket is special because you paid for it yourself."

    My sister and I were flying by ourselves from our home in Kansas to a summer camp in Minnesota. Our plane had a two-hour stop at the airport in Omaha, Nebraska. A flight attendant took us to a souvenir shop, where a toy airplane looked just like the plane my sister and I were flying on. I really wanted that airplane. I had $10 and the plane cost $8. I had no idea what I needed to buy at camp, but I bought the plane anyway. When we reached the camp, I discovered that there were no showers! Instead, we bathed in a lake every night. I needed to buy special soap because the regular soap I brought had chemicals that could harm the fish. The special soap cost $4 at the camp store. However, I had only $2 left.

    What upset me was that I couldn't get clean without the soap, which was soon found by my teacher, Sally. I had to tell her that I had spent most of my money on a toy airplane. She laughed and explained to me that a budget was necessary and it was a plan for spending money to help make sure you set aside enough for things you need, like soap, before you buy fun things, like toys.

    Sally gave me one of her extra(额外的) bottles of special soap. When I returned home, I decided to budget. I spent several weeks writing down everything I bought, just to get an idea of how I was already spending my money. Then I made my first weekly budget. My budget wasn't always the same each week. For some weeks, I would have more in my “Money In” account because I did some jobs around the house. Once summer vacation started, I didn't need to buy school lunches, so I had extra money to go to the neighborhood swimming pool or to give to the town animal shelter.

    Budgeting was hard, sometimes. Whatever week it was, I always made sure that “Money In” equaled “Save and Spend.” That's called making ends meet, and it's how you make sure that the money you have will always be enough to cover your plans to spend and save.

    Last year, I lived in Chile for half a year. I lived with a Chilean family and had the responsibilities of any Chilean teenager. I had good days and bad days I didn't understand.

    Chuquicamata, my host community, is a mining camp. When I arrived there, I was scared. It was so different from what I was used to. There were lots of dogs on the streets, and there was no downtown, few smoothly paved streets, and little to do for entertainment. Rain was not seen very often, earthquakes and windstorms were frequent.

    I had studied Spanish for two and a half years and was always one of the best students in my class. But in my first week in Chile I was only able to communicate and needed one person to whom I could explain my shock. I couldn't speak the thoughts in my head and there were so many.

    Most exchange students experience this like me. Culture shock presents itself in everything from increased aggression towards the people to lack of appetite (食欲). I was required to overcome all difficulties.

    As time passed, everything changed. I began to forget the words in English and to dream in Spanish and love Chilean food. I got used to not depending on expensive things for fun. Fun in Chuquicamata was being with people. And I took math, physics, chemistry, biology, Spanish, art, and philosophy.

    But the sacrifices were nothing compared to the gain. I learned how to accept and to succeed in another culture. I now have a deeper understanding of both myself and others.

    Washington, D.C. Bicycle Tours

    Cherry Blossom Bike Tour in Washington, D.C.

    Duration: 3 hours

    This small group bike tour is a fantastic way to see a world-famous cherry trees with beautiful flowers of Washington, D.C. Your guide will provide a history lesson about the trees and the famous monuments where they blossom. Reserve your spot before availability—and the cherry blossoms—disappear!

    Washington Capital Monuments Bicycle Tour

    Duration: 3 hours (4 miles)

    Join a guided bike tour and view some of the most popular monuments in Washington, D.C. Explore the monuments and memorials on the National Mall as your guide shares unique facts and history at each stop. Guided tour includes bike, helmet, cookies and bottled water.

    Capital City Bike Tour In Washington, D.C.

    Duration: 3 hours

    Morning or afternoon, this bike tour is the perfect tour for D. C. newcomers and locals looking to experience Washington, D.C. in a healthy way with minimum effort. Knowledgeable guides will entertain you with the most interesting stories about Presidents, Congress, memorials, and parks. Comfortable bikes and a smooth tour route(路线) make cycling between the sites fun and relaxing.

    Washington Capital Sites at Night Bicycle Tour

    Duration: 3 hours(7miles)

    Join a small group bike tour for an evening of exploration in the heart of Washington, D.C. Get up close to the monuments and memorials as you bike the sites of Capitol Hill and the National Mall. Frequent stops are made for photo taking as your guide offers unique facts and history. Tour includes bike, helmet, and bottled water. All riders are equipped with reflective vests and safety lights.