Geology of the National Parks

Wrap Up


Review the Unit 5 Introduction

You have reached the end of Unit 5! Double-check the list of requirements on the Unit 5 Introduction page and the Course Calendar to make sure you have completed all of the activities listed there.

Unit 5 Overview

Click here to review the Unit 5 Overview and make sure you understand all the main topics.

Review of the main topics and ideas you encountered in Unit 5.

Weather, Weathering, and Landslides

  • Sun hits equator straight-on, poles a glancing blow, so equator gets more sun.
  • Sun heats Earth, drives convection in the atmosphere.
  • On rotating Earth, this creates interesting winds including onshore breezes on US West Coast.
  • Winds rise up Coast Ranges and the Sierra Nevada, watering redwoods and sequoias.
  • Winds sink down into Death Valley, drying it.

Why Redwood Wet, Death Valley Dry?

  • Warmer air can hold more moisture.
  • Rising air expands and cools, sinking air is compressed and warms.
  • Evaporation requires heat (so you cool as sweat evaporates), and condensation releases heat.
  • Air cools 5oF for 1000 foot rise until condensation starts
  • Air cools 3oF for 1000 foot rise with condensation (formation of clouds and then snow or rain).
  • Air from the Pacific is wet, rises over Redwood and rains.
  • Dry air comes down the other side into Death Valley.
  • Air cools 3oF for 1000 foot rise going up, warms 5oF for 1000 foot fall coming down; for 15,000-foot-high mountains, air comes down 30oF warmer than it went up.
  • So Death Valley is hotter than Redwood (lack of clouds to shield Death Valley warms it further).
  • Air going from Redwood to Death Valley is heated when condensation releases the energy originally used in evaporating the water that rains out on Redwood.

Rocks Not Forever

  • Weathering=physical changes that make small rock pieces from big, and chemical changes that make new minerals.
  • Physical from crystal growth in cracks (especially ice), etc.
  • Common rock granite has quartz= silica (silicon+oxygen), feldspar=aluminum+silica+(calcium or sodium or potassium), dark mineral=iron+magnesium+silica; chemical weathering.
  • Quartz stays as quartz sand (little change).
  • Feldspar makes clay; calcium and sodium wash away.
  • Dark mineral makes rust; magnesium and silica wash away.
  • Rust+sand+clay+worm poop=soil.
  • Calcium and silica go to make shells in the ocean.
  • Magnesium reacts with hot sea-floor rocks
  • Sodium makes the ocean salty.
  • Soil eventually washed to ocean.
  • Subduction takes seawater, sediment, shells, and soils down to melt, rise, and solidify as granite in a nearly-balanced cycle.

Mass Movement

  • Mass movement is the downhill transport of soil, rock without rivers.
  • Mass movement ranges from huge, destructive landslides to barely measurable soil creep.
  • Rivers usually pick up material from mass movement and take it on.
  • Usually get a balance between soil production by weathering and soil removal, although humans are upsetting the balance in many places.
  • Can often figure out where mass movement is potentially destructive, and stabilize slopes or stay out of the way.

Reminder - Exercise #2 is due and Exercise #3 opens this week. See Course Calendar for specific dates and times.

Supplemental Materials

Following are some supplementary materials for Unit 5. While you are not required to review these, you may find them interesting and possibly even helpful in preparing for the quiz!

Comments or Questions?


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