Soil Sciences Overview

Soil Sciences

• Soils are a vital natural resource essential for agriculture and environmental management.
• Pedology studies soil formation, classification, physical, chemical, and fertility properties.
• Edaphology focuses on the influence of soils on plant growth and ecosystems.
• Agronomy involves crop production, biotechnology, and soil science applications.
• Hydrogeology examines groundwater distribution and transport through soils and rocks.

Topography

• Topography analyzes landforms and their evolutionary processes.
• Orography studies the distribution of mountains and topographic relief.
• Hypsometry measures the height and depth of physical features relative to mean sea level.
• Topography is essential for understanding physical features of the landscape.

Earthquake Dynamics

• Earthquakes occur when two blocks of the Earth's crust suddenly slip past each other.
• A fault (fault plane) is the surface where the slip occurs, and a hypocenter is the initial location of the earthquake beneath the surface.
• The epicenter is the point directly above the hypocenter on the Earth's surface.
• Foreshocks are smaller earthquakes that may precede a larger one; they cannot be identified until after.

Earth's Structure and Composition

• Earth is the third terrestrial planet, supporting life with a mean density of 5.5 g/cm³.
• Composed of three primary parts: Atmosphere, Lithosphere, and Hydrosphere.

Atmosphere

• The outer gaseous layer extends up to 700 km and retains minimal mass within the total Earth mass.
• It consists of multiple layers: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.

Lithosphere

• The rigid outer shell of Earth, composed of solid rock and extending from the surface downwards.
• Includes the crust (continental and oceanic), mantle, and core.

Hydrosphere

• Encompasses all natural water bodies on or below the Earth's surface, constituting 0.03% of Earth's mass.
• Critical for life sustainability.

Continental and Oceanic Crust

• Continental crust is characterized by three layers:
  • A Layer (2-10 km thick, sedimentary rocks)
  • B Layer (20 km or more thick, granite and gneiss)
  • C Layer (25-40 km thick, basaltic composition)
• Oceanic crust, generally 5-7 km thick, is extensions of the C layer.

Earthquake Recording and Measurement

• Seismographs record earthquakes, producing a seismogram.
• Energy from an earthquake releases seismic waves that propagate outward, causing ground shaking.
• Magnitude of earthquakes is determined by seismographic data, with variations in intensity based on location during the event.

Earth Structure Statistics

• Earth is described as an oblate spheroid, with:
  • Equatorial radius: 6378 km
  • Polar radius: 6357 km
  • Mean radius: 6371 km
• Surface area: 1.101 x 10^14 m², with 70.8% water cover and 29.2% land cover.

Core Composition

• Core consists primarily of nickel and iron, with an inner core being solid and outer core liquid.
• Temperatures range from 4,000°C to 7,000°C in the core, affecting tectonic activity.

Mantle Composition

• Mantle includes upper (5-50 km depth) and lower (720-2900 km depth) parts, with varying densities promoting plate tectonics.

Tectonic Plates

• When tectonic plates move, friction may cause them to get stuck, leading to energy accumulation until an earthquake occurs.

Key Term Definitions

• Fault Plane: Surface where blocks slip.
• Hypocenter: Initial earthquake location below the surface.
• Epicenter: Surface point above the hypocenter.
• Magnitude: Size of an earthquake determined by seismograph data.
• Foreshock: Smaller quake before a major quake.