Geology and Rock Types

Main Elements of Earth's Crust
- Primary elements include:
- Oxygen
- Silicon
- Aluminum
- These elements form the bulk of the Earth's crust, but it is noted that their percentages do not sum to 100%, thus indicating the presence of other elements as well.

Element Interaction
- When the main elements interact, they combine to form minerals.
Definition of Mineral:
- A mineral is defined as a naturally occurring inorganic crystalline solid.
- Minerals possess very particular chemical properties and have a distinct physical structure.
Field of Study:
- The study of minerals is known as Mineralogy.
- This field distinguishes the various families of minerals.
Common Mineral Family:
- The silicates are the most commonly found minerals due to their prevalence in the Earth's crust, stemming primarily from silica (SiO₂).
- Examples of silicate minerals include those found in gemstones.

Process of Rock Formation:
- Minerals aggregate to form rocks.
Definition of Rock Dust:
- Rock dust is an aggregate that can consist of one or multiple mineral types.

Classification of Rocks:
- There are three major types of rocks identified:
- Igneous Rocks
- Sedimentary Rocks
- Metamorphic Rocks
- All identified rocks belong to one of these three groups.

Formation:
- These rocks are formed from the cooling of molten rock called magma.
- Magma either rises to the surface (extrusive) or cools slowly underground (intrusive).
Types of Igneous Rocks:
- Intrusive Igneous Rocks:
- Formed when magma cools slowly underground; characterized by larger crystals due to slower cooling.
- Extrusive Igneous Rocks:
- Formed when lava erupts and solidifies on the surface; they generally have smaller, finer crystals.
Composition Categories:
- Mafic Rocks:
- Characterized by high iron and magnesium content; typically darker and denser (e.g., Basalt).
- Felsic Rocks:
- Rich in silica; lighter in color and less dense (e.g., Granite).
Common Examples:
- Basalt:
- Forms most of the Earth's oceanic crust; significantly dense and sharp.
- Granite:
- Commonly used in countertops; forms much of the continental crust.

Formation Process:
- Formed through sedimentation, cementation, compaction of other rock pieces or organic material.
Subtypes of Sedimentary Rocks:
- Clastic Sedimentary Rocks:
- Formed from fragments of other rocks (e.g., Sandstone, Mudstone).
- Non-Clastic Sedimentary Rocks:
- Formed through chemical precipitation (e.g., Evaporates like rock salt).
- Organic Sedimentary Rocks:
- Consist of biological debris (e.g., Limestone, Coal).

Formation Process:
- Result from heat and pressure changes in existing rocks (igneous, sedimentary, or metamorphic).
Characteristics:
- Typically occur at temperatures between 600°C-1,500°C without melting.
Examples:
- Gneiss:
- Formed from granite.
- Marble:
- Formed from limestone.

Concept Overview:
- The rock cycle describes the ongoing process in which each type of rock can transform into another through geological processes.
- All rocks can be traced back to magma that rises from below the Earth's surface.
- Geographical and geological processes can lead to remarkable landforms, including karst topography resulting from limestone dissolution.

Weathering and Erosion:
- Factors like water, ice, and wind wear down rocks and shape landscapes.
Distinct Features:
- Sedimentary rocks display distinct layering due to their formation processes, allowing the history of the Earth to be read within their layers.

The implications of collisions between oceanic and continental crusts.
The significance of sedimentary rocks in preserving ecological and geological history.