2 . Many people assume Egypt is, and always has been, a desert. But considering that climates and landscapes can change over time and that humans have been known to change natural environments, was ancient Egypt a desert?

The simple answer is no. Not all of Egypt, ancient or modern, qualifies as a desert. Areas near the Nile River tend to be lusher (草木繁茂的), and Egyptians — in both ancient and modern times — have had a successful system of agriculture. However, the environment has changed over Egypt’s history, and the construction of the Aswan High Dam (坝) across the Nile between 1960 and 1970 changed the landscape greatly.

Some areas of Egypt that are now desert were wetter in the past. One famous example is the “Cave of Swimmers” in southwestern Egypt. Today, the area is very dry, but thousands of years ago, it was wetter, and some of the rock art found in caves in the area appears to show people swimming, according to the British Museum.

The Aswan High Dam caused some areas in southern Egypt to flood, leading to the creation of Lake Nasser. Many people had to move, and some archaeological (考古的) sites ended up underwater. The construction of the dam also ended the natural flooding of the Nile. The creation of Lake Nasser also led to more moisture (水分) in the air in some areas of southern Egypt.

One effect of the generally higher Nile River levels during the Bronze Age is that around 2500 B. C., when the pyramids at Giza were constructed, the “Khufu branch”, a vanished (消失的) branch of the Nile River, came right next to the pyramids (金字塔). This branch allowed for materials to be transported to the site by boat, aiding in pyramid construction.

The ancient Egyptians who lived by the Nile in some ways viewed themselves as living on an island in the Nile Valley, with the deserts as a sort of great sea.

4 . The US government has recently helped people learn more about the dangers of earthquakes by publishing a map. This map shows the chances of an earthquake in catch part of the country. The areas of the map where earthquakes are most likely to occur are called earthquake belts. The government is spending a great deal of money and is working hard to help to discover the answers to these two questions:

Can we predict earthquakes?

Can we control earthquakes?

To answer the first question, scientists are looking very closely at the most active fault (断层) systems in the country, such as the San Andreas fault in California. A fault is a break between two sections of the earth’s surface. These breaks between sections are the places where earthquakes occur. But it will probably be many years before we can predict earthquakes correctly. And the control of earthquakes is even farther away.

However there have been some interesting developments in the field of controlling earthquakes. The most interesting development concerns the Rocky Mountain Arsenal earthquakes. Here water was put into a layer of rocks 4,000 metres below the surface of the ground. Shortly after this injection (注射) of water, there was a small number of earthquakes. Scientists have decided that the water which was injected into the rocks worked like oil on each other.

When the water “oiled” the fault, the fault became slippery and the energy of an earthquake was given out. Scientists are still experimenting at the site of these earthquakes. They have realized that there is a connection between the injection of the water and the earthquake activity. They have suggested that it might be possible to use this knowledge to prevent very big, dangerous earthquakes, that is, scientists could inject some kind of fluid like water into faults and change on a big earthquake into a number of small, harmless earthquakes.