CURSO UNAM 2023 GEOGRAFIA #3 | 1.3 Geografía física: El paisaje natural

Welcome and Course Overview

In this section, the instructor welcomes the students to the geography course for the UNAM exam and introduces the topics to be covered in this class.

Introduction to Geography

• The instructor encourages students to subscribe, like the video, and mentions that two classes are uploaded daily.

• Emphasizes the importance of subscribing to help channel growth and hints at where to find previous classes.

Physical Geography

• Discusses physical geography focusing on natural landscapes, including relief, water bodies, soil, planets, and climate.

• Mentions branches of physical geography such as geomorphology, biogeography, hydrogeography, oceanography, cartography, climatology, and edaphology.

Global Tectonics

• Introduces global tectonics discussing Earth's structure with a focus on the core, mantle (upper and lower), asthenosphere (mantle), and crust.

• Explains how these components relate to each other within Earth's structure.

Theories of Global Tectonics

This part delves into theories related to global tectonics including continental drift theory and seafloor spreading theory.

Continental Drift Theory

• Explores Alfred Wegener's theory of continental drift dating back approximately 180 million years when all continents were part of Pangaea.

• Details how continents moved due to convection currents under Earth's crust.

Seafloor Spreading Theory

Expanding Earth Theory and Plate Tectonics

In this section, the speaker discusses the Expanding Earth Theory and Plate Tectonics, explaining how the rotation of the Earth generates centrifugal force leading to the movement of continents.

The Forces Behind Plate Movements

• The rotation of the Earth generates centrifugal force, causing continents to move as if pushed by a force.

• John Tuzo Wilson and other geographers describe the lithosphere as a mosaic of plates moving due to centrifugal forces.

• Continents move on top of the upper mantle due to these forces, leading to phenomena like earthquakes.

Major and Minor Plates

• Major plates include North American, Eurasian, South American, Indo-Australian, Antarctic, and Pacific plates.

• Minor plates like Cocos, Caribbean, Nazca, Philippine, Arabian, Juan de Fuca are also significant in causing seismic activities.

Causes of Seismic Activities

This part delves into the causes of seismic activities such as plate tectonic collisions and volcanic eruptions.

Understanding Seismic Events

• Sismic events result from plate tectonic collisions and volcanic activities.

• Stress builds up during plate collisions leading to faults which cause subduction phenomena.

• Subduction occurs when one plate slides over another triggering earthquakes due to released energy.

Volcanic Activity and Risk Zones

The discussion shifts towards volcanic activity's impact on seismic events and identifying high-risk zones globally.

Volcanic Eruptions and Risks

• Volcanic eruptions can trigger earthquakes through gas release during magma ascent.

Exam Question on Seismic Zones in Mexico

The instructor discusses the seismic zones affecting Mexico, focusing on the San Andrés fault and the interaction between the Cocos and North American plates.

Seismic Zones Affecting Mexico

• The primary seismic zones affecting Mexico include:

• San Andrés fault.

• Collision of the Cocos plate with the North American plate.

• Impact on regions:

• States affected by resulting earthquakes: Michoacán, Guerrero, Oaxaca, Chiapas, and Mexico City.

• Emphasis on Michoacán, Guerrero, and Oaxaca for exam focus.

Conclusion of Class and Preview of Next Topics

The class concludes with a call to action for viewers to engage with upcoming topics related to landforms, population distribution, economic activities, and mineral resources.

Concluding Remarks

• Encouragement for engagement:

• Viewers urged to like and subscribe for support.

• Motivation to continue providing free educational content.

• Preview of upcoming topics:

• Distribution of prominent world and Mexican landforms.

• Relationship between relief forms, population distribution, and economic activities.