Earth’s Dynamics: Continents, Oceans, and Atmosphere
Continental Drift and Internal Forces
Continental Drift: The theory of continental drift posits that approximately 200 million years ago, Earth had a single supercontinent called Pangaea. This landmass subsequently broke apart, with the fragments (tectonic plates) gradually moving to their current positions.
Internal Forces: The Earth’s internal forces are responsible for phenomena such as earthquakes and volcanoes.
- Earthquakes result from vibrations or seismic waves within the Earth.
- Volcanoes are fissures in the Earth’s crust. Pressure causes magma to rise to the surface through these cracks. Volcanic eruptions expel gases, ash, rocks, and lava. The cooling of these materials forms the volcanic cone.
Continents and Relief
Continents: Continents are vast landmasses separated by oceans. There are six: Africa, America, Asia, Europe, Oceania, and Antarctica.
Continental Relief: The continental surface is varied, featuring mountains, plains, plateaus, and valleys.
The European Continent
Europe, a relatively small continent, is essentially a peninsula of the larger Eurasian landmass. It is surrounded by various oceans and seas. Key relief features include:
- The Great European Plain
- Plateaus and old mountain ranges
- Young mountain ranges
Water: Oceans, Seas, and Rivers
Salt Water (Oceans and Seas): Most of the Earth’s water is saline, comprising the oceans and seas. Oceans are large bodies of water separating continents, while seas are extensions of oceans near continental areas.
Fresh Water (Rivers): Fresh water exists in groundwater, lakes, rivers, icebergs, glaciers, and the atmosphere. River water is constantly in motion. The flow of a river is the volume of water it carries, and its flow regime describes variations in flow throughout the year. A river’s regime can be rainfall-based (flow affected by rainfall) or melt-based (water from melting snow). Rivers shape the landscape through erosion, transport, and sedimentation.
Ocean and Sea Movements
Ocean and sea water is in constant motion due to:
- Waves: Caused by wind moving the water’s surface.
- Tides: The rising and lowering of water levels, caused by the Moon’s gravitational pull.
- Ocean Currents: Large-scale movements of water, similar to rivers, that traverse the oceans.
The Atmosphere
The Atmosphere: A gaseous layer over 1000 km thick surrounding the Earth, protecting it from direct solar radiation.
The Ozone Layer: Ozone, a gas in the atmosphere, forms a layer that filters ultraviolet (UV) light. Contact with certain gases, often from industrial sources, can create holes in this layer, allowing harmful UV radiation to reach the Earth’s surface.
Atmospheric Temperature and Humidity
Atmospheric Temperature: The amount of heat in the air resulting from solar radiation. Factors influencing temperature include latitude, altitude, and proximity to the sea.
Air Humidity: Humidity refers to the amount of water vapor in the air. The air’s capacity to absorb water vapor depends on its temperature. A hygrometer is used to measure humidity.