Hydrologic Cycle and Earth's Systems Overview

Hydrologic cycle

Water moves between oceans, atmosphere, glaciers, rivers, groundwater, plants, and animals through processes like evaporation, precipitation, infiltration, runoff, and transpiration.

Water distribution on Earth

Oceans (97%), glaciers/ice caps (2%), groundwater (0.6%), surface water (0.01%), atmosphere (0.001%).

Stream discharge calculation

Discharge = cross-sectional area × velocity. It's important for flood prediction and water resource management.

Hydrograph

Rising limb (increasing discharge), peak flow, falling limb (decreasing discharge).

Stream flow characteristics downstream

Channel becomes wider and deeper; flow becomes faster; sediment size becomes smaller.

Stream channel changes over time

Through erosion and deposition — meanders migrate, oxbow lakes can form.

Velocity, erosion, and deposition around a meander

Fastest flow and erosion on the outer bend; deposition on the inner bend.

Braided vs meandering streams

Braided = multiple channels, coarse sediment, variable flow. Meandering = single, winding channel, fine sediment.

Flood prevention methods

Levees, dams, floodplain zoning, and early warning systems.

Porosity

% of open space in a material.

Permeability

Ability to transmit water.

Porosity and permeability by material

Sands/gravel = high both. Clays = high porosity but low permeability.

Water table

The top of the saturated groundwater zone.

Groundwater system entry and exit

Enters through infiltration. Leaves via springs or pumping wells.

Groundwater flow and pollution

It flows from high to low pressure; pollutants travel along groundwater flow lines.

Formation of oil and gas

Organic material buried under sediment is heated and compressed over millions of years.

Oil and gas reserves

In porous reservoir rocks capped by impermeable layers.

Formation of coal

From compressed swamp plants buried under sediment layers.

Non-fossil fuel energy sources

Solar, wind, hydroelectric, geothermal, nuclear.

Electricity generation

By spinning turbines that turn generators.

Main energy source for electricity in the U.S.

Natural gas.

Greenhouse gases

Greenhouse gases trap infrared radiation, warming Earth.

Climate models

Continued warming, sea-level rise, more extreme weather — depending on emissions.

Ways to reduce warming

Use renewable energy, capture carbon, plant trees, increase efficiency.

Earth's compositional layers

Crust, mantle, outer core (liquid), inner core (solid).

Plate tectonics

Earth's lithosphere is broken into moving plates floating over the asthenosphere.

Geologic processes at plate boundaries

Divergent: plates pull apart (seafloor spreading), Convergent: plates collide (mountains, volcanoes), Transform: plates slide past (earthquakes).

Observations

Something you notice or measure.

Hypothesis

Testable idea to explain observation.

Prediction

What will happen if the hypothesis is correct.

Element

One type of atom.

Compound

Chemically bonded elements.

Mineral

Naturally occurring crystal structure.

Rock

Aggregated minerals.

Volcanic and plutonic rocks

Felsic: Granite (plutonic), Rhyolite (volcanic); Mafic: Gabbro (plutonic), Basalt (volcanic).

Types of magma formation

Mid-ocean ridge: Decompression melting; Subduction zone: Water-lowered melting point; Hotspot: Mantle plumes.

Types of sedimentary rocks

Clastic = Sandstone; Chemical = Rock salt; Biochemical = Limestone.

Earthquake hazards

Ground shaking, landslides, liquefaction, tsunamis, aftershocks.

Magma viscosity controls

High silica = thicker magma; High temperature = runnier magma.

Predicting volcanic eruptions

Monitor earthquakes, ground deformation, and gas emissions.

Earth's uniqueness for life

Presence of liquid water, atmosphere, magnetic field, and plate tectonics.

Atmospheric composition and climate

Greenhouse gases trap solar heat.

Factors influencing global temperatures

Greenhouse gases, solar variability, volcanic activity, ocean currents.

Climate proxies

Ice cores show past atmospheric gases; Tree rings show growth related to climate; Ocean sediments show temperature patterns.