Day 8 notes

Louis Lackey

Day 8 Notes

Chapter 7- Earth and the terrestrial worlds

Section 7.1-Earth as a planet

Mercury is covered in craters, with smooth plains and cliffs. Venus has few craters but many volcanoes. Mars has some volcanoes and craters, and possibly riverbeds. The moon has craters and smooth plains. Earth has volcanoes, craters, mountains, and active riverbeds. Why have these planets turned out so differently even though they formed at the same time from the same materials?

The earth is geologically active because of the differences of the interior layers, the core, mantle, and crust. The denser material goes to the middle, and the lithosphere is the cool, rigid space that floats on the warmer, softer rocks. The lithosphere is a different amount of the mantle from planet to planet. The earth's core is made of nickel and iron, the mantle of silicon and oxygen, etc, the crust is granite, basalt, etc. We assume that other planets are similar to earth.

Heat drives geological activity, convection causes the mantle to rise and fall, this cycle takes 100 million years. This heat comes from the gravitational potential energy from accreting planetesimals, the friction of differentiation, and radioactivity. Accretion and differentiation were more forceful when the planet was young, today radioactivity is the most important heat source. It cools from convection, conduction, and radiation from the center to the crust, and into space. Smaller objects cool faster, and surface area.

Heat causes moving particles in the earth's core to create a magnetic field. The earth's magnetosphere protects us from charged particles from the sun, and also creates the aurora.

The processes that shape the surface of a planet are cratering, volcanism, tectonics, and erosion.

Section 7.2- The moon and mercury, geologically dead

Section 7.5- Earth as a living planet

Liquid water, oxygen atmosphere, plate tectonics, and climate stability are unique to earth and necessary conditions to support life.

Plant's photosynthesis is required to make high concentrations of oxygen, which produces 0v3 ozone. Plate tectonics are also an important step in the carbon dioxide cycle.

Atmospheric COv2 dissolves in rainwater, rain erodes minerals into the ocean, and the minerals combine with carbon to make rocks on the ocean floor. Subduction carries carbonate rocks down to the mantle, and the rocks melt and out-gases COv2 back into the atmosphere.

Changes in the earth's tilt might lead to ice ages. Ice lowers global temperatures by increasing reflectivity. Frozen oceans increase COv2 out-gassing, raising temperatures again.

Human activity has caused global temperature to rise to its highest recorded levels. CFC's destroy the ozone. Human exploitation is driving other species to extinction. The use of fossil fuels produces greenhouse gases that can cause global warming.

A habitable planet must be located at an optimal distance from the sun for liquid water to exist. It must be large enough for geological activity to release and retain water and atmosphere.