Earth’s Dynamic Systems: Atmosphere, Tectonics, and Life’s Origins
The Earth: Atmospheric Changes
Some minor gases control climate and life. For example, water vapor, carbon dioxide, and methane are greenhouse gases, transparent to visible radiation from the sun but opaque to infrared. These gases trap heat emitted from the Earth, raising the Earth’s surface temperature over 30ºC. Without them, half of the atmosphere’s temperature would be -18ºC.
- Main components of the atmosphere: Nitrogen 78.1%, Oxygen 20.9%, and Argon 1%.
Why is There Liquid Water on Earth’s Surface?
- Earth is closer to the Sun than Jupiter’s satellites.
- Earth’s greater mass creates atmospheric pressure that limits water evaporation.
- The presence of greenhouse gases in the atmosphere.
The Interior of the Earth
The Earth’s core consists of 80-90% iron and 10% nickel. The heat of the inner core keeps it in a liquid state. This heat comes from colliding objects that heated up, causing planetesimals to melt due to violent clashes. Probably much of the heat from deep in the heart comes from this process.
Seismic Waves
Seismic waves caused by earthquakes cross the interior of the planet and, as with sound, change their direction and speed when the medium through which they spread changes. S-waves (which do not propagate in fluids) are no longer transmitted at 2900 km, indicating that they have found a layer that we call the fluid outer core.
Evidence of Continental Drift
- Geographical Evidence: Wegener suspected that the continents might have been united in the past, observing a great overlap between the shapes of the coastlines of continents. Where these continents had once been united into one (Pangea), the pieces fit.
- Paleontological Evidence: Pertaining to fossils, paleontological studies indicate that these prehistoric organisms would have been unable to cross the oceans that separate these continents today. This test indicates that the continents were assembled in a bygone era.
- Geological and Tectonic Evidence: It can be seen that the types of rocks, their timing, and major mountain ranges have physical continuity.
- Paleoclimatic Evidence: There were areas on Earth whose current climates differed from those they had in the past. Currently, hot areas were covered with ice, while at that time, North America and Europe had warm woods.
Fragmented Lithosphere
The energy inside the Earth manifests in the form of heat and earthquakes. If you notice the seismic sources and volcanoes on a map, it appears that most of these are not randomly distributed but are aligned. This suggests the idea of a large, fragmented lithosphere composed of lithospheric plates.
How Did the Plates Form?
The rocks were volcanic seafloor. If you look at the ages of rocks, there is a curious symmetry. In the mid-ocean ridge, volcanic rocks are younger, and their age increases symmetrically on both sides of the ridge.
Conclusion: There are ridges in volcanic materials that are emerging from inside the Earth, adding to and expanding the oceans’ lithosphere.
Plate Tectonics
This theory explains the history and geological processes on Earth. It proposes that the thermal store located in the core heats the mantle sufficiently for current conversion to occur: hot materials rise and cool down. This thermal motion moves the lithosphere, breaking it into plates.
Lithosphere in Motion
The Atlantic is now 30 feet wider than when Columbus crossed it. Elsewhere, the plates collide and generate orogens (mountain ranges) of the continental margin, such as the Andes, or intracontinental, like the Himalayas. In these zones, the oceanic lithosphere is destroyed when introduced into the mantle, a process called subduction.
Creation and Destruction of Relief
Because of the low density of thickened continental crust, orogens are under the effects of a float, raising further as the chain is eroded. Material erosion of the mountain leads to a new elevation of the crust until its thickness is normal. With the float removed, the orogen stops rising, and erosion flattens it: the continents are shaped by these ancient orogens and are drawn, called cratons, which contain the oldest rocks on Earth. The destruction of the relief is made by progressive erosion of the cortex. The orogen stops rising, and erosion flattens it, so the continents are just plain old. Despite this continuous erosion, the internal dynamics of the planet generate new reliefs. While there is internal energy and convection, new reliefs will continue to be generated.
The Prescription of Life (C, H, O, N)
Living matter is composed of elements that constitute a majority: hydrogen, oxygen, and carbon. 98% of our body is water and carbon; the other 2% is smaller proportions of iron (manufactures hemoglobin), selenium (without which our liver would stop working), sulfur (a component of hair and nails), and potassium (without which nerve impulses would be discontinued).
- Example (the apple): Water: 85%, Carbohydrates (carbon compounds): 14%, Salts and other elements: 1%
Energy for Life
It is made by plant photosynthesis, algae, and some bacteria. Depending on where you get the organic matter, you may be autotrophic (plants) or heterotrophic (us).
The Origin of Life
Where does the carbon come from? Inside the Earth, which accumulated when our planet formed.
Where does the water come from? The best hypothesis is from asteroids whose orbits are brought from beyond that of Mars.
Order the Origin of Life
- Photosynthetic marine organisms
- Marine invertebrates
- Invasion of the terrestrial environment
- Marine animals with shells
- Lungfish
- First reptiles
- Evolution of reptiles, conifers appear
- First dinosaurs
- Early birds
- Dinosaur extinction
- Flowering plants
- Mammal domain (1st monkeys)
- Homo sapiens
Genetic Drift
An evolutionary force that acts in conjunction with natural selection by changing the characteristics of species over time.
Evolutionary Radiation
If the continents were united, species would tend to be eliminated by competition, and life would be impoverished. By contrast, when a dispersed Pangea appears (more continents), there will be new environments (more expensive, for example), and the number of species increases.
True or False Question: Looking at the different layers of pyrite, it followed that before there was oxygen, which is false because there was no oxygen. (This statement is self-contradictory and requires further clarification or context.)
What is the origin of Homo sapiens? Homo heidelbergensis.