How Can Physical Processes Affect Settlements?
Earth's physical processes, such as volcanoes, desertification, and earthquakes, can have major impacts on human settlements. As populations grow and population densities increase, the impacts from these processes will affect more and more people.
WHY DO YOU THINK PEOPLE CHOOSE TO LIVE IN A PLACE WHERE THESE DANGERS EXIST?
As you explore this page, list the potential threats of each physical process, the reasons why people settle in areas where these threats exist, and the steps that people take to deal with these threats: How Can Physical Processes Affect Settlements?
V O L C A N O E S
Most of Earth's volcanoes are found in the Ring of Fire, an area that circles the Pacific Ocean, as shown in this map.
Why settle in a place like this?
PROS:
- Many metals, such as gold, silver, and copper, are found in volcanic rock. This is good for mining, and providing jobs.
- Soils around volcanoes are rich in minerals, making them good for farming.
- Homes near volcanoes can have a natural hot-water supply from geothermal energy.
- Volcanoes are cool, and tourism is an important part of local economies.
CONS:
- When they erupt, they release lava, gas, and ash that can damage settlements and cause injury or death
LESSEN THE THREAT / RESPOND:
- Early-warning systems
- Evacuation plans
E A R T H Q U A K E S & T S U N A M I S
The map of the Ring of Fire above shows that many large urban areas are on or near plate boundaries. As urban areas grow,more people are at risk during earthquakes.
Many earthquakes occur below oceans and can cause devastating tsunamis, or huge surface waves. All coastal settlements in earthquake zones are in danger.
The largest earthquakes don't always cause the most damage and loss of life. The amount of damage depends on whether the area affected is densely populated, the strength of the structures, and the emergency measures in place.
Why settle in a place like this?
PROS:
- Earthquakes often occur along tectonic plate boundaries, which tend to be on coasts, but coasts provide access to shipping, fishing, and natural beauty
CONS:
- destruction of property and loss of life
- tsunamis can wash away coastal settlements
LESSEN THE THREAT / RESPOND:
- Conduct earthquake drills
- Prepare shelters, emergency kits, and evacuation plans
- Build buildings that limit the damage from earthquakes
D E S E R T I F I C A T I O N
This map shows existing deserts and areas that are at risk of becoming deserts. Over 100 countries are losing their drylands to desertification.
Desertification: the gradual process of turning drylands into desert.
Drylands: areas that have semi-desert to moist climates and long growing seasons. These areas make up 41 percent of Earth's land area.
Drought worsens desertification because it directly affects soil quality. Long-term drought reduces moisture in the soil, causing the soil to become dry and thin. The soil then becomes loose and blows away, changing to area into desert.
Desertification is widespread and affects hundreds of millions of people worldwide. The loss of arable land in an area can change settlement patterns there. Long-term drought is threatening food production in Africa's Sahel region. This problem is so severe that people are leaving their homes.
THE GREAT GREEN WALL PROJECT
Long-term drought has caused China's large deserts--the Taklamakan and Gobi deserts--to expand. Over 400 million people are now at risk.
To slow desertification, the government has planted shrubs, grasses, and trees along the edges of the deserts. These plantings are called shelterbelts, and they prevent soil erosion. This project has slowed the desertification rate by about 40 percent since the 1990s.
DUST STORMS
Dust storms are a consequence of desertification. They're common in the Sahara Desert in Africa and in the deserts in China. The dust raised can blow up to 8 km high, adding dust to the atmosphere. This wind can damage equipment and buildings, as well as damage human skin and eyes, and even cause breathing problems.
Dust storms can also have a positive impact. Winds can drop the dust thousands of kilometers from where it was picked up. The soils in Central and South American rainforests get most of their mineral nutrients from dust that came from the Sahara Desert in Africa.
Why settle in a place like this?
PROS:
- Land may have once been fertile (the reason people settled there in the first place)
CONS:
- loss of arable land
- dust storms damage equipment, buildings, and human health
LESSEN THE THREAT / RESPOND:
- Plant shelterbelts to prevent erosion
- Irrigate to provide moisture to the soil
L A N D S L I D E S
WHAT CAUSES A LANDSLIDE?
When there's too much water on a slope, the land can slide or flow down the slope, creating a landslide or a mudslide. Settlements near steep slopes covered by clay, sand, or silt are in the most danger. Landslides can result from natural causes, such as heavy rains, melting snow, and earthquakes.
Human activities can also cause landslides. Tree roots help to keep the land in place on slopes; clearing away too many trees makes the land unstable. Also, when roads are built on slopes, the supporting land is sometimes removed which can make the earth unstable. During rainy seasons, the heavy rain and lack of supporting land can cause a landslide.
Why settle in a place like this?
PROS:
- Land at the top of a rise often has spectacular views
- Land at the base of a rise often provides protection from elements
- Other land is not available
CONS:
- destruction of settlements and loss of life
LESSEN THE THREAT / RESPOND:
- Construct barriers against slides
- Reinforce embankments
- Plant trees and grasses to strengthen embankments
- Keep dangerous areas off-limits for settlement and activities
- Communities can also try to direct water away from these areas