The Handy Geography Answer Book. Paul A Tucci

quarantine areas and where to focus treatment efforts.

      Which natural disasters doesn’t southern California experience?

      Urban southern California is plagued by many natural disasters, including earthquakes, wildfires, floods, landslides, and tornadoes. Thankfully, they rarely receive snowstorms or hurricanes.

      What causes wildfires to occur?

      Approximately 10% of all wildfires are caused by lightning that ignites material and forms a wildfire. Experts at the U.S. Park Service assert that the remaining 90% of all wildfires are started by human activity, like campfires, the burning of trash, discarded cigarettes, and arson.

       How can I learn more about disasters in my town?

      Each community should have its own disaster plan that includes a history of past disasters (those that have happened in the past are likely to occur in the future) along with plans for dealing with future disasters. You should be able to consult this plan to learn how your community would cope with disaster and to find out the locations of evacuation routes and shelters. Many communities place important disaster-planning information online for easy reference.

VOLCANOES

      How are volcanoes formed?

      Volcanoes are the result of magma rising or being pushed to the surface of the Earth. Hot liquid magma, which is located under the surface of the Earth, rises through cracks and weak sections of rock. The mountain surrounding a volcano is formed by lava (called magma until it arrives at the Earth’s surface) that cools and hardens, making the volcano taller, wider, or both.

      What is the difference between magma and lava?

      Magma is hot, liquefied rock that lies underneath the surface of the Earth. When magma erupts or flows from a volcano onto the Earth’s surface, it becomes lava. There is no difference in substance; only the name changes.

      What is the Ring of Fire?

      If you were to look at a map of the world’s major earthquakes and volcanoes, you would notice a pattern circling the Pacific Ocean. This dense accumulation of earthquakes and volcanoes is known as the Ring of Fire. The ring is due to plate tectonics and the merger of the Pacific Plate with other surrounding plates, which creates faults and seismic activity (especially Alaska, Japan, Oceania, and coastal North and South America), along with volcanic mountain ranges, such as the Cascades of the U.S. Pacific Northwest and the Andes of South America.

      The Ring of Fire encircles the Pacific Ocean with volcanic and earthquake activity.

      How many active volcanoes are there in the world?

      There are about 1,500 potentially active volcanoes around the world, but the number often depends on how we define active. Experts at the National Geographic Society consider approximately 1,900 volcanoes on Earth to be active, with evidence of activity and a strong likelihood to explode again. Most are located in the Ring of Fire surrounding the Pacific Ocean. About one-tenth of the world’s active volcanoes are located in the United States. A volcano is considered active if it has erupted in the last 10,000 years. If you were to consider how many volcanoes may be at the bottom of the sea floor, there could be many thousands more.

      What are some of the world’s most active volcanoes, in terms of numbers of years of eruptions?

      The volcanoes that have been active the most number of years include Mt. Etna in Italy (3,500 years), Mt. Stromboli in Italy (2,000 years), and Mt. Yasur in Vanuatu (800 years).

      How many active volcanoes are located in Europe?

      There are more than sixty active volcanoes in Europe and more than forty dormant ones, many of which are located in Italy, Sicily, and Greece.

      Which volcano poses the most risk to people in Europe?

      Mt. Vesuvius, on the southwestern coast of Italy, lies very near a city of more than one million people: Naples. Although it last erupted in 79 C.E., it is still active, and geologists predict there is a very good chance it will erupt again, potentially putting the city of Naples and the surrounding area at risk.

      How many active volcanoes does Iceland have?

      Iceland, formed by volcanoes, lies between two tectonic plates along the Mid-Atlantic Ridge and is home to approximately 130 volcanoes. Of these, 30 are considered to be active.

      Where are the active volcanoes in the United States?

      Alaska, Washington, Oregon, and California have many potentially active volcanoes. The most recent large-scale eruption in the United States was that of Mt. St. Helens in southern Washington State in 1980. Other volcanoes in the region, such as Mt. Shasta, Mt. Lassen, Mt. Rainier, and Mt. Hood, could erupt with little warning.

      What is so interesting about volcanoes in Alaska?

      Alaska contains approximately 130 volcanoes, with 90 that have been active in the last 10,000 years. Volcanoes in the state of Alaska account for over 75% of all volcanoes that have erupted in the United States in the last two hundred years.

      The ruins of Pompeii attract tourists today, but it is difficult to imagine the horror of an entire city wiped out by a volcano.

      How was Pompeii destroyed?

      In the year 79 C.E., the volcano Mt. Vesuvius erupted and buried the ancient Roman town of Pompeii under 20 feet (6 meters) of lava and ash. Pompeii is famous because excavations of the city, which began in 1748 and continue to this day, provide an excellent look at Roman life at the beginning of the millennium. The covering of the city by debris preserved not only the places where people last stood but also paintings, art, and many other artifacts. The nearby city of Herculaneum was also buried and perfectly preserved. Although a much smaller version of Pompeii, it contains some of the best art, architecture, and examples of daily life in Roman times and is only twenty minutes away from Pompeii. Even loaves of bread that were baking on the day of the eruption are preserved in a nearly 2,000-year-old bakery.

EARTHQUAKES

      What creates earthquakes?

      The tectonic plates of the Earth are always in motion. Plates that lie side by side may not move very easily with respect to one another; they “stick” together, and occasionally they slip. These slips (from a few inches to many feet) create earthquakes and can often be very destructive to human lives and structures.

      What is an epicenter?

      An epicenter is the point on the Earth’s surface that is directly above the hypocenter, or the point where earthquakes actually occur. Earthquakes do not usually occur at the surface of the Earth but at some depth below the surface.

      What is a fault?

      A fault is a fracture or a collection of fractures in the Earth’s surface where movement has occurred. Most faults are inactive, but some, like California’s San Andreas Fault, are quite active. Geologists have not discovered all of the Earth’s faults, and sometimes earthquakes occur that take the world by surprise, like the one that occurred in 1994 in Northridge, California. When earthquakes occur on faults that were previously unknown, they are called blind faults.

      What is the significance of the infamous San Andreas Fault?

      The infamous San Andreas Fault lies at the border between the North American and the Pacific tectonic plates. This fault is situated in California and is responsible for some of the major earthquakes that occur there. Los Angeles is on the Pacific Plate, but San Francisco is on the North American Plate. The Pacific Plate is sliding northward with respect to the North American Plate, and, as a result, Los Angeles gets about half an inch closer to