Notes, summaries, assignments, exams, and problems for Geology

Background to the Land of Continental Drift

During the nineteenth and twentieth centuries, the prevailing theory was contractionism. It proposed that the Earth, as it cools, contracts, resulting in large folds of the crust. This was later referred to as fixism.

The Wilson Cycle

The Wilson Cycle describes the cyclical process of ocean basin formation and destruction. It consists of the following stages:

1. Continental Fragmentation: Begins with the fragmentation of a continent by a hot spot. Magma from the mantle rises, causing a bulging of the lithosphere.
2. Formation of a Rift Valley: The lithosphere breaks, forming parallel faults. Central blocks sink by gravity, creating the Rift Valley.
3. Formation of a Young and Narrow Sea: Magma ascends from the

Factors That Determine the Shape of Relief:

• The Type of Rock: Every rock has specific characteristics.
• Climate: The type of external geological agent that dominates an area is determined by the climate.
• The Structure of Materials: Rocks that have been folded or fractured provide an initial way.
• Relief Seniority: External geological agents remove materials from one place and deposit them in others.

Clay Reliefs: However, in arid climates with little vegetation, poor but torrential rains originate a dense network of gullies and ravines called badlands. Karst Reliefs: Reliefs arising from the dissolution of limestone or other similar rocks are known as karst relief. Forms of Karst: Rainwater dissolves the surface of the limestone and forms small furrows... Continue reading "Understanding the Factors Influencing Relief Shapes" »

Aridity: Regional Water Scarcity

Features of regions with water shortages due to rainfall insufficiency, where evaporative water loss or evapotranspiration exceeds atmospheric water contributions via precipitation. Example: Periods of aridity in Spain.

Mountain Climate Characteristics

Climate characterized by low temperatures compared to surrounding plains, with high rainfall, sometimes in the form of snow in the most elevated parts. Example: Navacerrada has a mountain climate.

Mediterranean Climate Features

Temperate climate characterized by relatively mild, wet winters and hot, dry summers. Rainfall is most frequent during autumn and spring. It is characteristic of the coasts of the Mediterranean basin. Example: Climate of the Balearic Islands,

Evolution

Fixism

Species remain unchanged.

Creationism

Species are divinely created.

Lamarckism

Species change over time. Proposed by Lamarck. Assumptions: environmental conditions vary, creating changes and modifications.

Darwinism

Survival of the fittest drives species change.

Key Concepts in Evolution

Fossils

Remains of organisms that lived on land and are now extinct.

Geographical Distribution

A common ancestor lived on a continent, and upon separation and isolation, species evolved independently.

Homology

Similarity due to a common ancestor.

Embryonic Development

Vertebrate embryos are very similar at early stages due to a common ancestor.

Molecular Genetics

Comparing DNA to determine kinship.

Mutations

Changes in genetic material that can be beneficial, detrimental,... Continue reading "Evolution and Environmental Factors in Biology" »

Cosmic and Terrestrial Phenomena Explained

Cosmic Origins: Why We Are Stardust

We are stardust because calcium, oxygen, and almost all elements are compounds derived from the explosion of a star.

Stellar Lifespans: Why Massive Stars Burn Faster

Bigger stars last less time because they deplete their fuel faster than less massive stars. Their greater mass accelerates fuel consumption proportionally.

Evidence for the Big Bang Theory

One of the most important tests confirming the veracity of the Big Bang theory was provided by astronomer Vesto Slipher. He analyzed the light spectrum of the most distant galaxies and observed that their light waves invariably had a peculiar elongation. To understand the significance of these observations, one must understand... Continue reading "Unveiling the Universe: Stars, Planets, and Earth's Dynamic Past" »

Continental Drift and Plate Tectonics

Mechanism of Continent Movement

• The concept suggests oceanic sliding; the ocean floor remains motionless.
• Lithospheric plates slide over the mantle as the continents move. The oceanic floor changes.

Forces Driving Continent Movement

• Not clear. One mechanism suggests Earth's rotation could be the cause of motion.
• Mantle convection currents. Seafloor spreading at the ridges pushes the continents.

Causes of Reliefs

• Wrinkles produced in the leading edge of continents.
• Lithospheric plate collisions.

Oceanic and Continental Lithosphere

• Thickness

  • Oceanic: 100 km
  • Continental: 300 km

• Crust Composition

  • Oceanic: +90% of its mass are basaltic metamorphic rocks. Rocks poor in quartz.
  • Continental: +85% of its mass are granitic metamorphic

There are three major morphostructural groups:

1. Antique Beds: Made up of mountains of medium height, flattened summits (peneplains), consisting of material folded in the Paleozoic era, deformed by Hercynian and Alpine folding.

2. The Alpine Mountains: These are very young and high; their basic material is limestone.

3. Depressions: These can be of different types:

• Some fragments are located on the old sunken Hercynian base, such as the Cuenca del Duero.
• Others occupy former inlets or bays that are silting up by sediments from the Alpine ranges, such as the depression of the Ebro and Guadalquivir.

Mainland Units and Dynamic Stresses

The fundamental unit is the Meseta peninsular relief, which is an area of highlands (600-800 m) divided into two sectors... Continue reading "Major Morphostructural Units and Relief Dynamics of Spain" »

Properties of Minerals

Physical Properties

Exfoliation: The property of minerals to split along a preferred direction. These minerals have a weaker union between each crystalline unit. It depends on the internal structure of the crystal and is constant for each mineral. The following grades are usually distinguished: excellent, perfect, good, very flawed, and imperfect.

Fracture: When a mineral fractures, the chemical bonds are broken irregularly, unrelated to the symmetry of the structure.

Toughness: The resistance of a mineral to being scratched. It depends on the chemical bonds. Its value is calculated by comparing it with other minerals of known hardness (Mohs scale).

Specific Gravity: A number that expresses the relationship between the mineral'... Continue reading "Mineral Properties: Physical, Optical, and Chemical Characteristics" »

Geological Origin: Plate Movement

The relief units in the Iberian Peninsula are composed of layers of rock that have been folded or fractured. All these changes are caused by plate tectonics. The geological history of Spain is conditioned by the interaction of two plates: the Eurasian and African plates.

• Precambrian or Archaic Era

  (Started ~4 billion years ago) A set of lands emerged from the sea, with outcrops consisting of gneiss and slates in what are now the Central System and the Montes de Toledo. These were later eroded and covered by the sea. The Iberian Peninsula formed a vast geosyncline where materials were deposited.

• Primary or Paleozoic Era

  (Started ~600 million years ago) The first major orogeny occurred: the Hercynian orogeny. After

Agglomerated Materials Defined

Stones, sand, and similar substances are materials that possess the property of adhering to other materials, forming what are known as mortar and concrete pastes. These materials are molded into their final form and subsequently harden.

Agglomerative Material Classification

Aerial Materials

These are materials that harden in the air and are not water-resistant (e.g., gypsum, aerial lime).

Hydraulic Materials

These harden both in air and in water (e.g., hydraulic lime, Portland cement).

Bituminous Materials

These are liquid or viscous hydrocarbons that harden by evaporation of their solvents or by cooling (e.g., asphalt cement).

Types of Gypsum

• Gypsum Dihydrate (CaSO₄·2H₂O): The most abundant form found in quarries.