Earth's Geology: Rocks, Minerals, and Ocean Dynamics

Earth's Geological Foundations

Understanding Rocks

Igneous Rocks

Igneous rocks are formed when magma solidifies.

Magma Defined

Magma is a mixture of molten rock and gases.

Metamorphic Rock Classification

Metamorphic rocks are classified, often exhibiting laminar (layered) or crystalline structures.

The Rock Cycle Explained

The rock cycle is the set of processes experienced by rocks and sediments at the surface and inside the Earth's crust.

Uses of Rocks

• Building materials
• Ornamental purposes
• Containers
• Fuel
• Chemical industry

Minerals and Their Properties

Minerals: Definition and Features

Solid minerals are formed by the chemical combination of elements in the Earth's crust. Rocks are composed of minerals, which possess three key features:

• Being natural
• Having inorganic origin
• Having homogeneous chemical composition

Carbon Forms: Diamond vs. Graphite

Diamond is pure carbon, formed in Earth's interior under enormous pressures and high temperatures.

Graphite is also pure carbon, but its formation process differs.

Key Mineral Properties

• Color
• Luster
• Hardness
• Streak color
• Cleavage

Methods of Mineral Extraction

Opencast Mining

This method is used when the deposit is shallow. Soil and rock layers are dug to reach the area of interest. It can be:

• Quarries: for superficial deposits
• Open-pit mines: for deeper deposits

Underground Mining

Used when the deposit is at great depth. Involves tunnels, vertical shafts, and horizontal galleries that branch off to reach areas of interest. Mine work is particularly dangerous, and galleries require shoring to prevent landslides.

Ocean Dynamics and Water Bodies

Three Types of Ocean Movements

Waves

Waves are oscillations that occur in surface water due to wind action. They have several effects:

• Mixing
• Erosion
• Transport

Currents

Currents are movements of water masses in the ocean that flow like rivers. They are caused by three factors:

• Prevailing winds
• Temperature differences
• Salinity differences

Tides

Tides are the periodic rise and fall of sea water, produced by the gravitational attraction of the Moon and, to a lesser extent, the Sun.

Terrestrial Water Systems

Intermittent Streams (Wadis/Arroyos)

These are watercourses that are dry for part of the year. In arid areas, they are dry riverbeds that can remain dry for years. During periods of intense rainfall, water flows through them with violence, making them very dangerous.

Wetlands, Marshes, and Swamps

These are areas where the soil remains waterlogged throughout the year. Water depth is highly variable and may be saltwater if they are near the coast.

Water Movement Processes

Surface Runoff (Exorheic Flow)

Surface runoff is the movement of water across the Earth's surface, forming rivers and streams.

Infiltration

Infiltration is the penetration of surface water into the ground (subsurface). It is more efficient when the soil is porous.