The Earth's History Flashcards
How is Earth Structured?
Earth has a differentiated crust, meaning that different layers have different properties. This is the main feature that makes our planet dynamic. This allows the Earth to evolve with mountains, oceans, volcanoes.
What is Differentiation with Planets?
When planets formed by accretion, they start off homogenous. The earth and other terrestrial planets do not remain this way - they become differentiation or internally layered.
How does Differentiation Occur?
To be accomplished, the earth must be heated and partially melted. When this happens, heavy metals (like iron and nickel) would move downward to form a dense core. Less dense material would form around the core. Lighter material would separate out around this later, forming the uppermost crust.
Does the planet need to be completely melted or can it just be partially melted?
It just needs to be partially melted.
Where does heat come from to accomplish the melting of planets?
Some of the heat to accomplish melting comes from impacts during earths accretion, some comes from Radioactive Decay, and some is produced by gravitational compression.
What is Radioactive Decay?
Some isotopes are not stable, they decay over time to stable isotopes. The time it takes half of the material to decay is called the half-life. When an isotope decays, it produces a particle (radiation and energy). This energy is the source of the heat. This continues to occur until a stable atom is left.
How is heat produced by gravitation compression?
As the earth becomes larger, the pull of its gravity increases. This reduced the size of the Earth and adds heat.
Describe the Internal Structure of the Earth.
The core is made up primarily of nickel and iron. Divided into a solid inner core and liquid outer core. The mantle is rocky and divided into different layers.
What is the Earth’s Lithosphere?
The Earth’s crust and upper mantle.
What is the Earth’s Asthenosphere?
The asthenosphere is in the high mantle and has a slushy mixture of solid and melted rock.
What is the division between the crust and mantle called?
The Mohorovicic Discontinuity (Moho).
What is the composition of the Continental crust?
Light and thick.
What is the composition of the Oceanic crust?
Thin and dense.
