esci 402 midterm

Atoms, Elements, and Molecules:

• Atoms: The basic building blocks of matter, made up of protons, neutrons, and electrons.

• Elements: Pure substances consisting of only one type of atom. Each element is defined by the number of protons in its nucleus (atomic number).

• Molecules: Combinations of two or more atoms bonded together.

Minerals:

• Definition of a Mineral: Naturally occurring, inorganic solids with a definite chemical composition and a crystalline structure.

• Silica Tetrahedron: The basic building block of silicate minerals, consisting of a silicon atom surrounded by four oxygen atoms in a tetrahedral shape.

• Silicate vs. Non-Silicate Minerals:

  • Silicate minerals contain silicon and oxygen. Examples include quartz and feldspar.

  • Non-silicate minerals do not contain silicon-oxygen tetrahedra. Examples include carbonates, sulfates, and halides.

Chemical and Dynamic Layers of the Earth:

• Chemical Layers:

  • Crust: The Earth's outer layer, made of lighter rocks like granite (continental) and basalt (oceanic).

  • Mantle: Located beneath the crust, composed mostly of silicate minerals rich in iron and magnesium.

  • Core: The innermost layer, consisting of a solid inner core made of iron and nickel and a liquid outer core.

• Dynamic Layers:

  • The lithosphere (rigid outer layer, including the crust and upper mantle).

  • The asthenosphere (a more fluid, ductile layer beneath the lithosphere).

  • The mesosphere (the lower mantle).

  • The outer core (liquid) and inner core (solid).

Rocks:

• Igneous Rocks: Formed from the cooling and solidification of molten rock (magma or lava).

  • Texture: Based on the size of mineral crystals (e.g., coarse-grained or fine-grained).

  • Composition: Can be classified as felsic (rich in silica), intermediate, mafic (rich in iron and magnesium), or ultramafic.

  • Bowen’s Reaction Series: Describes the sequence in which minerals crystallize from cooling magma.

  • Stability of Minerals: Some minerals are more stable under certain temperature and pressure conditions.

• Metamorphic Rocks: Formed from the alteration of existing rocks due to heat, pressure, or chemically active fluids.

  • Foliation: The alignment of mineral grains in a rock under pressure.

  • Types: Examples include slate, schist, and marble.

• Sedimentary Rocks: Formed by the accumulation and compaction of sediments.

  • Clastic: Made from fragments of pre-existing rocks (e.g., sandstone).

  • Non-clastic: Formed from chemical processes or biological activity (e.g., limestone).

  • Roundness, Sorting, Composition: Describes the texture and grain size of the rock particles.

  • Weathering, Transport, Deposition: The processes that break down rocks and move particles to form sediments.

  • Depositional Environments: Locations where sediment accumulates (e.g., riverbeds, deserts, oceans).

  • Sedimentary Structures: Features like bedding, ripple marks, and cross-bedding.

Fossils:

• Importance as Geologic Tools: Fossils help in dating rocks and understanding past environments.

• Preservation Requirements: Rapid burial and the right conditions (e.g., anoxic environments) are essential for fossilization.

• Types of Preservation: Includes petrification, amber, and molds/casts.

Plate Tectonics:

• Types of Plate Boundaries:

  • Convergent: Plates move toward each other, often forming subduction zones (e.g., oceanic plates diving beneath continental plates).

  • Divergent: Plates move apart, creating spreading ridges (e.g., Mid-Atlantic Ridge).

  • Conservative (Transform): Plates slide past one another (e.g., San Andreas Fault).

• Wegener & Continental Drift: Alfred Wegener proposed that continents were once connected in a supercontinent called Pangaea and have since drifted apart.

• Apparent Polar Wander: Evidence that the Earth's magnetic poles have moved over time, supporting continental drift.

• Mid-Ocean Ridges and Seafloor Spreading: New oceanic crust is formed at divergent boundaries, creating the mid-ocean ridges.

• Magnetic Sea Floor Stripes: Symmetric patterns of magnetic anomalies on either side of mid-ocean ridges, supporting seafloor spreading.

• Driving Forces of Plate Tectonics: Convection currents in the mantle, slab pull, and ridge push.

• Earthquakes and Volcanoes: These geological features often occur at plate boundaries, providing evidence for plate tectonics.

Principles for Relative Age Dating:

• Original Horizontality: Layers of sediment are originally deposited horizontally.

• Lateral Continuity: Layers of rock extend laterally until they thin out or are interrupted by other features.

• Superposition: Older layers are found beneath younger layers.

• Cross-Cutting Relationships: Features that cut across rocks (like faults) are younger than the rocks they cut through.

• Inclusions: Pieces of rock (inclusions) found in another rock are older than the rock they are in.

• Faunal Succession: Fossils occur in a predictable sequence in the geologic record.

• Unconformities: Gaps in the geologic record, representing periods of erosion or non-deposition.

Disturbance and Deformation of Rock Strata:

• Types of Stress:

  • Tensional Stress: Stretching of the crust (occurs at divergent boundaries).

  • Compressive Stress: Squeezing of the crust (occurs at convergent boundaries).

  • Shear Stress: Sliding of rock layers (occurs at transform boundaries).

• Folds: Bends in rock layers caused by compressional stress (e.g., anticlines and synclines).

• Faults: Fractures where rocks have moved relative to each other. Types include normal, reverse, and strike-slip faults.
  Principles for Relative Age
  Original horizontality, lateral continuity, superposition, cross-cutting relationships, inclusions, faunal
  succession, unconformities
  Disturbance and deformation of rock strata
  Types of stress
  Folds and Faults