Earth’s Dynamics, Natural Hazards, and Resource Management
Earth: A Dynamic Planet
Earth is a dynamic planet where changes occur, some cyclically, i.e., repeated periodically.
- Heat from the sun falling on the air makes it rise. Its place is occupied by colder air, and this produces atmospheric currents. By heating the water, the hydrologic cycle starts (evaporation, condensation, and precipitation) and, similar to the atmospheric currents, produces ocean currents (oceanic conveyor belt).
- The core of the Earth warms the planet’s interior, and convection produces currents: the cold materials fall and the hot ones rise, which feeds volcanoes that release into the atmosphere compounds of carbon, sulfur, and nitrogen (important for climate and the biosphere).
The dynamism of the Earth and variations in temperature and climate influence the biosphere, originating in massive extinctions on occasions.
Inherent Risks of Earth’s Dynamics
A) Rain – Floods are the natural phenomenon that causes the most victims. The erosion caused by rain impoverishes the soil. Landslides can be caused by heavy rains (or earthquakes). In areas with dense vegetation, rain is absorbed by the ground, avoiding or limiting its adverse effects.
B) Earthquakes, Tsunamis, and Volcanoes
- Earthquakes, originated by the movement of lithospheric plates, produce vibrations in the soil that can collapse constructions. There are certain construction procedures that limit the impact of earthquakes.
- Tsunamis are waves caused by sudden deformation of the sea (a submarine landslide can cause a tsunami). These waves travel at high speeds, are not very high (less than 1 m) but very long. When they reach the coast, water accumulates to a height of 10-15 m.
- Volcanic eruptions produce lava flows that are not usually dangerous unless gases are released suddenly in the form of very hot clouds (glowing avalanches) or fall on the riverbed, forming a mudflow.
Science Predicts and Prevents
Meteorologists predict (each time with greater precision) the weather, providing useful warnings about adverse conditions (possible snow, storms, floods, etc.).
Seismologists study the movements of the Earth’s crust, indicate areas where risks are high, and where precautions must be taken in the construction of buildings.
Volcanologists prepare volcanic risk maps and publish information for the inhabitants of volcanic areas.
Oceanographers conduct studies on the structure, flora, and fauna of the oceans and have developed systems for detecting tsunamis.
Risk maps indicate the areas where there is some likelihood of the occurrence of a destructive natural phenomenon. They must be taken into account when planning the construction of housing or public works.
Humans Exploit the Land
Human beings use the land’s resources (food, drink, building materials, energy, etc.). It is necessary to be aware that these resources are limited.
A) Reserves – These are deposits of rocks, minerals, and metals that have not yet been exploited. For the moment, the reserves of any relevant material have not been exhausted. However, their low price has increased for some of them.
B) The Problem of Food – The industrial revolution produced an increase in the population, which caused an increase in the demand for food that was solved by allocating forests to field crops. The Green Revolution (mid-20th century) increased agricultural productivity through the mechanization of the field and the use of fertilizers and pesticides. At present, further studies using transgenics are increasing productivity. 800 million people go hungry in the world.
Overfishing is catching fish at a rate greater than they are able to reproduce. One in three species that were fished in 1950 is in danger of extinction.
Deforestation is the cutting of trees to use the space they occupy for farmland, cities, means of communication, etc. With deforestation, the danger of erosion and desertification appears.
Forestry is the rational exploitation of forests.
C) The Problem of Water – Water is a limited resource. Over-exploitation leads to the depletion of aquifers. Water availability is increased by the construction of reservoirs, water transfer, the construction of desalination plants, and wastewater treatment and reuse.
D) Energy Sources
Hydroelectric: The reservoir is used to move turbines. Movement between a magnet and a conductor generates an electric current.
- Advantages of reservoirs: Reservoir water can be used for human consumption, irrigation, and producing electric power. Dams prevent dangerous floods.
- Disadvantages: Flooded areas of the riverbanks, destabilize deltas, and disrupt aquatic life.
Nuclear: The reactions of nuclear fission (breaking atomic nuclei) release heat that is used to vaporize water. This moves turbines, generating electric current.
- Advantages: High energy production from small quantities of fuel.
- Disadvantages: Radioactive waste is generated, which is very dangerous and long-lasting.
Wind: The wind moves the blades of the mills, which in turn move turbines that generate electricity.
- Advantages: A clean and renewable energy.
- Disadvantages: The energy efficiency is low.
Solar: The heat of the sun is directly converted into energy in solar panels or evaporates water. The generated vapor is used to move turbines.
- Advantages: This is a renewable and clean energy.
- Disadvantages: The energy efficiency is low.
Biofuels: These are combustible products produced from biological materials.
- Advantages: They can replace oil.
- Disadvantages: Land devoted to biofuel production stops producing food, thus increasing their price. In addition, they are contaminants.
Hydrogen: Hydrogen (H2) reacts with oxygen (O2) and produces water and energy. Oxygen is obtained from the air; hydrogen is obtained by the decomposition of water using solar panels.
- Advantages: It is a renewable and clean energy.
- Disadvantages: The solar panels used to split water are expensive and not very efficient.