Earth’s Systems and Landforms
Earth’s Systems
The ground system consists of interrelated subsystems:
- Atmosphere: The gaseous layer surrounding Earth. It contains gases like oxygen, protects us from space radiation, and influences surface changes.
- Hydrosphere: All the water on the planet. Oceans comprise 97% of the total water.
- Biosphere: All living beings, ranging from high altitudes to the deep ocean and underground.
- Geosphere: Earth’s surface and interior. Physical and chemical phenomena release energy, impacting other subsystems.
Earth’s Internal Structure
Seismic wave discontinuities reveal Earth’s interior isn’t uniform but composed of concentric layers with different chemical properties. The Gutenberg and Mohorovicic discontinuities separate the crust, mantle, and core. Changes in seismic wave velocity indicate layers with varying mechanical properties: the lithosphere, asthenosphere, and core.
Plate Tectonics
Plate tectonics theory posits that Earth’s surface is divided into rigid lithospheric plates sliding on the soft asthenosphere. These plates move at approximately 1.7 cm per year, interacting along their boundaries, causing earthquakes, volcanic eruptions, and mountain formation. There are three types of plate boundaries:
- Divergent boundaries: Plates move apart, allowing magma to emerge, creating mid-ocean ridges.
- Convergent boundaries: Plates collide. Oceanic-continental collisions form subduction zones, trenches, and mountain ranges. Continental-continental collisions create extensive mountain ranges.
- Transform boundaries: Plates slide past each other. Friction can cause sudden energy release, leading to earthquakes.
Terrestrial Landforms
Earth’s surface features are known as relief. There are two types: continental and oceanic.
Continental Relief
- Mountains: Rocky outcrops with steep slopes and a peak.
- Mountain Range (Cordillera): A series of connected mountains.
- Valley: An elongated depression between mountains.
- Canyon: A steep-walled cleft between mountain ranges.
- Hills (Sierras): Low-altitude mountains.
- Plateau: An elevated, flat surface.
- Plain: A low-level surface with slight inclination.
- Depression: A surface below sea level.
Oceanic Relief
- Continental Shelf: Gently sloping extension of the continent under the sea.
- Continental Slope: Steep area from the shelf to the abyssal plain.
- Trench: Deep, narrow cavity in subduction zones.
- Abyssal Plain: Flat, deep seabed with sediment accumulation.
- Oceanic Ridge: Submarine ridges with tectonic activity.
Relief-Shaping Processes
Land relief is shaped by:
- Endogenous (internal) forces: Cause large-scale crust deformation, mountain formation, volcanic eruptions, and earthquakes.
- Exogenous (external) forces: Erosion by rivers, wind, seas, rain, and glaciers.
Weathering
Weathering is the fragmentation of rock. It can be:
- Physical: Rock fracture without chemical changes.
- Chemical: Rock breakdown due to chemical reactions.
Denudation
Denudation involves erosion, transport, and deposition of materials.