WEEK 2: ROCKS AND TECTONICS

• Learning Goals:

  • Define mineral

  • List the three major types of rocks and explain how these rocks can be related to one another through the rock cycle

  • Explain why fossils typically occur in sedimentary rocks

  • Apply understanding of rock types to identify locations where dinosaur fossils might be found

  • Understand plate tectonics and how it affects different rocks

  • Compare Mesozoic continental configurations with modern configurations

What is a Mineral?

• Characteristics of a mineral:

  1. Naturally occurring

  2. Crystalline structure

  3. Solid state

  4. Definite chemical composition

  5. Usually inorganic

• Common minerals examples:

  • Copper

  • Pyrite (Fool's Gold)

  • Halite (Salt - NaCl)

  • Quartz (SiO2)

What is a Rock?

• Definition: A rock is a consolidated aggregate of minerals forming a significant part of the Earth's surface.

• Types of Rocks:

  • Igneous: Formed from magma.

  • Metamorphic: Formed under heat and pressure from pre-existing rocks.

  • Sedimentary: Formed through the accumulation and lithification of sediment.

Distinguishing Between Rocks

• Rocks can be distinguished based on:

  • Mineralogy (types of minerals present)

  • Texture (size and arrangement of mineral grains)

Igneous Rocks

• Formation:

  • Result from the cooling and solidification of molten rock (magma).

  • Can erupt on the surface (extrusion) or solidify below it (intrusion).

Sedimentary Rocks

• Formation Process:

  1. Erosion of materials transported by water.

  2. Sediments are deposited in layers in calm environments (e.g., lakes, river valleys).

  3. Over time, sediments are compacted and cemented through lithification.

  4. Types of Sedimentary Rocks:

  • Shale/Mudstone (from clay; low energy environments)

  • Sandstone (from sand; medium energy)

  • Conglomerate (from gravel; high energy)

Metamorphic Rocks

• Formation:

  • If buried deeper, sedimentary rocks can undergo metamorphism due to temperature and pressure changes, resulting in metamorphic rocks.

  • Metamorphic rocks can be uplifted and eroded, contributing to the rock cycle.

Fossils in Sedimentary Rocks

• Dinosaur fossils typically found in:

  • Sedimentary Rocks

• Fossilization Process:

  • Bones can be transported as sediments, become buried, and undergo lithification.

  • Quick burial is crucial for preservation.

Environments of Deposition for Fossils

• Fossil-preserving environments include:

  • Quiet water (lakes, lagoons)

  • Glacial environments

  • Swamps

• Grain sizes indicate energy levels:

  • Clays = low energy

  • Sands = medium energy

  • Gravels = high energy

The Layers of the Earth

• Structure based on composition:

  • Crust

  • Mantle

  • Core

• Physical properties:

  • Lithosphere (rigid outer layer)

  • Asthenosphere (ductile layer beneath lithosphere)

Plate Tectonics

• Lithosphere is broken into plates that move on the asthenosphere.

• Types of Plate Boundaries:

  • Convergent: Plates come together (subduction zones)

  • Divergent: Plates move apart (e.g., mid-ocean ridges)

  • Transform: Plates slide past each other (e.g., San Andreas Fault)

• Plate movements cause tectonic activity affecting the rock cycle, evolution, and fossil preservation.

Historical Context of Plate Tectonics and Fossils

• During the Mesozoic:

  • Early: All continents together (low sea level)

  • Late: Continents separate (high sea level)

• The configuration influenced dinosaur evolution and geographical distributions.

In-Class Assignment

• Finding Dinosaur Bones: Explore areas where sedimentary rocks, particularly those formed in low-energy environments, might preserve fossils.