Cosmology, Plate Tectonics, and Earth Dynamics

Expansion of the Universe:
- The universe continues to grow continuously over time.
- Within just a few seconds ( $t = \text{a few seconds}$ ) after the origin of the universe, nature's smallest building blocks were formed.
Composition of Matter:
- Everything seen in the surrounding environment is constructed from the exact same fundamental chemical elements.
- These elements were originally synthesized and formed inside stars.
- Examples of biological structures made up of these star-formed elements include human skin, hair, and teeth.
Galaxies:
- A galaxy is defined as a massive collection of a very large number of stars.
The Big Bang Theory (Big Bang-teorien):
- According to the Big Bang theory, it was predicted that it should be possible to measure the remnant radiation left behind from the Big Bang.
- Theoretical Accuracy: No theories about the universe have ever successfully predicted physical phenomena with such high accuracy as the Big Bang theory has achieved.

Divergent Plate Dynamics:
- At divergent boundaries, tectonic plates move away from each other.
Magma Upwelling and Ocean Floor Crust Formation:
- Magma flows upward from the mantle (mantelen) at a mid-ocean ridge (midthavsrygg).
- As the magma reaches the surface, it cools, solidifies, and becomes brand-new oceanic crust.
- This newly formed ocean floor pushes outward on both sides, forcing the tectonic plates further apart from each other.
Geographic Example — Mid-Atlantic Ridge:
- The Mid-Atlantic Ridge (Atlanterhavsryggen) is a primary example of a divergent plate boundary.
- It is located between Europa/Afrika and Nord/Sør-Amerika.
- Island (Iceland) sits directly on this ridge system.

Subduction Dynamics:
- When a tectonic plate meets and collides with a neighboring plate, one plate moves underneath the neighboring plate.
- The force of gravity actively pulls the subducting plate down into the mantle.
Formation of Deep-Sea Trenches:
- Underwater, the pulling down of a tectonic plate creates extreme oceanic depressions known as deep-sea trenches (dyphavsgrøfter).
Geographic Example — Mariana Trench:
- The Mariana Trench (Marianegropen) is the world's deepest point.
- It is situated where the Pacific Plate (Stillehavsplaten) is pulled down underneath the Philippine Sea Plate (Den filippinske platen).

Transform Boundary Dynamics:
- At transform boundaries, tectonic plates slide laterally past each other (sidelangs).
- Plates can also slide past each other horizontally in opposite directions.
Seismic Vulnerability:
- Areas along transform plate boundaries are heavily exposed to frequent earthquake activity.
Geographic Example — California:
- California in the USA is a prominent geographic example of a region situated along a transform sliding boundary.

Prehistoric Supercontinent:
- A continent named Laurentia existed $550\text{ million}$ years ago.
- Laurentia was composed of Nord-Amerika (North America) and Grønland (Greenland).
Earth's Layered Structure:
- The Earth's mantle lies directly between the continental tectonic plates (jordskorpen) and the Earth's core (kjerne).
- Tectonic plates float and move on top of the softer upper portion of the mantle.
Thickness of the Earth's Crust:
- At its thinnest locations (oceanic crust), the crust measures $5\,\text{km}$ thick.
- On average, the crust measures $30\,\text{km}$ thick.
Mountain Building (Fjellkjede) and Structural Proof:
- Tectonic forces and plate interactions form mountain ranges (fjellkjeder).
- Geological Proof: Professionals who work with mountains analyze exposed structural rock layers stacked on top of one another to observe the exact mechanisms by which the mountain was uplifted and pushed upward.
Mantle Convection Mechanisms:
- Over periods of millions of years, material inside the mantle flows in slow, continuous motion.
- Thermal Convection Mechanism: Warmer regions within the mantle rise upward, while colder regions sink downward, driving this extremely slow thermal convection cycle.