Geologic Time
How old is the Earth?
4.6 Billion Years Old
What percent Oxygen does today's atmosphere have?
~20%
What is the molecule for water (how do we write water using elements on the periodic table)?
H2O
What kind of nebula did Earth come from?
Planetary Nebula
Which layer is the densest layer?
the inner core
When did the first life forms develop on Earth AND WHAT were they called?
~ 3.4 Billion Years ago
Blue-green algae OR Cyanobacteria
List 2 gases that volcanoes produced during Earth's 2nd atmosphere.
Any TWO: Water Vapor, Carbon dioxide, carbon monoxide, methane, ammonia
What produced water vapor in Earth's early atmosphere?
Volcanoes
What is the principle of superposition?
A principle of relative dating that says rocks that lay on top of other layers are younger than the layers beneath.
What are Earth's 4 layers?
crust, mantle, outer core, & inner core
What event on the timescale marked the astonishing increase in complex life forms on Earth?
Cambrian Explosion
Explain how oxygen was able to build up in the atmosphere?
blue-green algae started photosynthesizing, which produces oxygen
What element was oxidized to the color red in the oceans? (formed layered rocks)
Iron (Fe)
At what time did Earth's crust form?
~ 100 million years after Earth formed OR 4.5 billion years ago
The crust is broken into 2 types. What are they?
Continental and Oceanic
When were most Banded Iron Formations created?
between ~1.8 - 2.5 billion years ago
Why were Hydrogen and Helium lost during the early stages of Earth's History?
The sun's radiation was too strong and the Earth's gravity was too weak to keep those light gases in the atmosphere
What are 3 theories for how water came to Earth?
1. icy comets
2. asteroids
3. water inside earth's rocks (in mantle)
Using the words ISOTOPE & HALF-LIFE, describe what radiometric dating is.
Radiometric dating uses isotopes that decay over time. Their decay rate depends on its half-life, the time it takes 1/2 of the parent isotope to decay.
Describe convection currents in the mantle. Use density in your answer.
the inner core's heat moves upwards, warming the mantle. Warmer material then rises to the top of the mantle because it becomes less dense. Then it cools, sinking back down to the bottom part of the mantle.
In what era did the dinosaurs live?
Mesozoic
What are the 5 layers of Earth's atmosphere?
Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere
What process led to Earth getting its oceans?
Water vapor built up in the atmosphere from volcanoes. As the Earth cooled, the water vapor condensed into liquid water.
Why did Earth's interior form layers?
density
The weak layer made up of the lower part of the upper mantle. This layer flows over time and is beneath the lithosphere, which is rocky and more rigid.