Earth’s Dynamic Equilibrium: Natural Hazards and Resource Management
Earth’s Dynamic Equilibrium
Heating and Density
The sun heats the Earth’s surface, warming the surrounding air. The core heats the planet’s interior. This uneven heating creates density differences, causing less dense materials to rise.
Water Cycle
The water cycle, powered by solar energy, distributes heat throughout the world’s oceans. This oceanic current cycle is sometimes called the “oceanic conveyor belt.”
Mantle Movements and Volcanoes
Mantle movements cause the ascent of deep materials, fueling volcanoes. Volcanoes expel gases trapped inside the planet.
A Dynamic System
These flows and cycles create a dynamic system with delicate balances. The Earth’s temperature is constantly changing.
Natural Hazards
Hazards of Rain
Floods are a major natural disaster. Streets flood due to overflowing rivers and streams, sometimes called ramblas in the Mediterranean area. These floods occur when channels cannot handle intense rainfall.
Heavy rains also exacerbate erosion.
Coastal floods are caused by storms. Hot seawater heats the air, which rises rapidly. This reduces pressure on the sea surface, causing it to rise. Combined with high winds, this generates waves up to 5 meters high, called storm surges, which inundate coastal lowlands.
Landslides occur when materials fall down steep slopes, often triggered by earthquakes, heavy rains, or rock type.
Earthquakes, Tsunamis, and Volcanoes
Earthquakes happen when the ground vibrates due to the movement of lithospheric plates, particularly at destructive plate margins.
Tsunamis are waves caused by sudden seabed deformations. These waves travel at speeds up to 800 km/h. While small at sea (around one meter), their long wavelengths carry enormous volumes of water. Upon reaching the coast, the water accumulates, creating waves 10 to 15 meters high that can penetrate several kilometers inland.
Volcanic eruptions involve lava flows, which are usually not dangerous. However, viscous magmas can clog a volcano’s vent, creating pressure. When the pressure exceeds the vent’s strength, the volcano erupts, releasing hot gas and magma particles in pyroclastic flows (hot clouds). If these flows encounter a riverbed, they can transform into lahars, resembling wet cement.
Predicting and Preventing Hazards
Meteorologists, seismologists, volcanologists, oceanographers, and geomorphologists work to predict and prevent natural hazards.
Risk maps are crucial for regional planning, guiding decisions about activities in different areas based on their risks.
While Spain’s seismic risk is low, weather-related disasters like floods, droughts, and desertification are significant concerns.
Increasing Consumption, Limited Resources
Population growth has led to increased per capita consumption of natural resources. The Earth’s carrying capacity is the maximum number of people it can sustainably support.
Rocks, Minerals, Metals: Will They Last Forever?
When a material becomes scarce, its price rises. Sometimes, substitutes are found. For example, fiber optic cables, made of plastic, have replaced many copper communication cables.
The Green Revolution and Its Consequences
The Green Revolution, with DDT, fertilizers, mechanization, and irrigation, significantly increased agricultural output, supporting the growing population during the industrial revolution.
Overfishing has led to the near-disappearance of many species.
Deforestation converts forests into cities, pastures, farmland, and roads. This loss includes not only vegetation but also soil, leading to desertification. Sustainable forestry practices offer an alternative.
A Problem with Water
Water consumption varies greatly. Some consume 320 gallons daily (64% agriculture, 24% industry, 12% domestic), while others have much less. Low water prices in some countries contribute to higher consumption.
Key water problems include aquifer depletion, coastal aquifer salinization, and the need for new reservoirs.