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

Earth's Interior: Composition and Structure

Sudden and Gradual Changes in Earth's Layers

There are both sudden and gradual changes within Earth's interior. These variations occur because materials differ in their composition and/or hardness. Since S waves propagate through solids but not fluids, we can conclude that at approximately 2900km depth, there is a transition to a continuous layer of molten material.

Ocean Floor and Magnetic Stripes

It was discovered that the oceanic crust, specifically basalts, and the associated bands had a magnetization parallel to the axis of the ridge. To explain these magnetic stripes, F. Vine and D.H. Matthews developed the theory of seafloor spreading. This theory posits that ridges are places where new oceanic... Continue reading "Earth's Interior: Composition, Structure, and Plate Tectonics" »

Atmospheric Dynamics: Vertical Movements and Stability

Convection

Vertical movements occurring in the troposphere, called convection, are caused by variations in temperature, humidity, or atmospheric pressure.

• Thermal Convection: These movements are caused by the contrast in air temperature. Air near the surface tends to rise, forming thermals of rising air, while higher up, the air tends to cool and descend.
• Moisture Convection: These are caused by the presence of water vapor in the air. Water vapor can be measured in two ways:

1. Absolute Humidity: The amount of water vapor in a determined volume of air, expressed in g/m³.
2. Relative Humidity: The amount of water vapor in 1m³ of air, expressed as a percentage, in relation to the maximum amount it can

What Are Fossils?

Places with rocks containing marine animal fossils were once under the sea. These organisms lived in the sea; upon dying, their bodies were deposited on the seabed and subsequently buried by sediments. Mountains are not as old as the Earth itself. When the organisms that became these fossils were alive, the rocks that now contain them (and form the mountains) might not have existed as mountains yet.

Explaining Marine Fossil Presence in Mountains

The presence of marine fossils in mountains can be explained by two main processes, both of which have occurred throughout Earth's history:

Changes in Sea Level

• Variation in the volume of water in the oceans: Climate has changed many times throughout Earth's history, affecting global sea

Humidity

The amount of water vapor present in the atmosphere.

Sotavento (Leeward)

The side sheltered from the wind; the opposite of windward.

Windward

The side facing the wind.

Glacial Valley

Characterized by a U-shaped cross-section or trough, which in geomorphology is seen as the main feature differentiating these types of channels, formed by the movement or sliding of an ice tongue.

Bay

An inlet of the sea into the coast.

Archipelago

A general term for a group or chain of islands.

Coastal Breeze

A gentle movement of air that occurs in coastal locations, blowing from the sea or from land.

Zocalo (Geological Shield)

Plains and plateaus formed in the primary era as a result of the devastation by erosion of mountain ranges encountered during the orogeny of... Continue reading "Essential Geographical and Geological Terms" »

Water Diversity: Elements of the River System

Water is an essential element for life, but only 3% is freshwater, with the rest being saline.

The Rivers

Rivers are continuous streams whose flow empties into lakes, other rivers, or seas.

Droughts and Floods

• Droughts: Periods of low flow.
• Floods: Periods of high flow.

Flow Rate

The volume of water in a river is measured in cubic meters per second.

The River Regime

The river regime expresses flow rate. Climate variations and the relief condition the rivers, also influenced by lithology, vegetation density, and human action.

Key Elements Affecting River Systems

1) Flow Rate

Flow is greater at the mouth of the river, where there is little evaporation.

2) Irregularity

This refers to the varying amount of water present... Continue reading "Understanding River Systems: Characteristics and Elements" »

Global Effects

The Greenhouse Effect

The greenhouse effect is the retention in the atmosphere of a portion of the heat emitted by the Earth's surface after it has warmed due to solar radiation. This process delays the release of thermal energy into outer space.

The concentration of gases in the atmosphere causes average temperatures on our planet to be around 15°C. Without these gases, it would be much colder. The main gas that absorbs terrestrial radiation is CO2, but water vapor also plays an important role.

Computer simulations predict significant changes by the end of the twenty-first century:

• An increase of between 1.5 and 6.5 ºC in average temperature.
• Changes in global rainfall patterns, with a tendency towards drought in some areas and

Key Factors Influencing the Climate of the Iberian Peninsula

Latitude: Situated between 35º and 43º North, the Iberian Peninsula lies within the temperate zone, experiencing four distinct seasons. Location: Nestled between the Atlantic Ocean (more open and cooler) and the Mediterranean Sea (smaller, enclosed, and warmer). Water bodies cool and heat more slowly than continents, so the coasts are affected by the sea's thermoregulatory effect, preventing excessively high temperatures. Influence of the Sea: Relatively low, with continental influence being more significant. The Peninsula behaves climatically like a small continent; the land cools and heats rapidly, leading to significant temperature variations both daily and annually. In winter,... Continue reading "Climate Factors and Atmospheric Dynamics in the Iberian Peninsula" »

Earth's Structure and Dynamics

Geochemical Modeling

• Crust: A rigid layer, either continental or oceanic.
• Mantle: Includes the upper mantle, transition zone, the Repetti discontinuity, and the Gutenberg discontinuity.
• Core: The outer core is distinguished by its properties.

Dynamic Model

• Lithosphere: Formed by the crust and the lithospheric mantle.
• Asthenosphere: Located between 100-250 km depth.
• Mesosphere: Located between 250-2900 km. Hot spots, thermal plumes, and feathers originate in this layer.
• Endosphere: Located between 2900-6371 km.

Plate Tectonics

Plate tectonics can be summarized as follows:

• The lithosphere is not a continuous layer but is divided into lithospheric or tectonic plates.
• Lithospheric plates rest on the asthenosphere, whose plasticity

Maria Luisa Group

These sites are located 23 km west of the Guri Dam. It includes four reservoirs, which are: a) Silver Hills Vallese and b) Peak Cerro Paja; c) Cerro Viejo and Cerro Black; d) Cerro Mataje.

Represent a reserve of 258 million metric tons and a tenor of 47% mineral.

Quadrilateral El Pao

Here we find the following sites:

• Site of El Pao: located 40 km southeast of the confluence of the Orinoco and Caroni rivers. Extension of 8600 hectares and reserves are 25 million metric tons.
• The Imperial (El Castillo): is located 56 km northeast of El Pao. The Crane is highlighted; its proven reserves are 27 million metric tons of iron ore.

Imataca Ring

These deposits are located, basically, in Delta Amacuro. Piacoa and Manoa stand out, which have... Continue reading "Venezuela Iron Ore, Bauxite, and Gold Sites" »

The Mountainous West of Argentina

The Andes

The western region of Argentina is dominated by the Andes Mountains, one of the world's most significant mountain systems. The term "Andes" encompasses a vast array of high mountains and plateaus. The immense pressure exerted during the Andes' uplift affected older geological structures, dislocating and incorporating them into the mountain range. This process also impacted pre-existing formations like the foothills of La Rioja, San Juan, and Mendoza, as well as the Pampean Ranges.

Sub-Andean Sierras

The Sub-Andean Sierras are relatively young, low-lying mountains, reaching heights of around 2,500 meters above sea level. They stretch north to south, their peaks sharply eroded by rivers and heavy rainfall.... Continue reading "Argentina's Mountainous West: A Journey Through the Andes" »