AP Environmental Science Unit 4: Earth Systems
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1
What materials make up Earth’s core, and why is it hot?
Iron and nickel — radioactive decay releases heat
2
What drives mantle convection?
Heat from core — warms magma
3
What is magma and why does it rise?
Molten rock — becomes less dense when heated
4
What is the asthenosphere and what role does it play?
Semi-molten soft rock — allows tectonic plates to move
5
What is the lithosphere?
Rigid outer layer — broken into plates
6
What is Earth’s crust?
Outer solid layer — top of lithosphere
7
How do plates move at divergent boundaries?
They separate — rising magma forces them apart
8
What features form at divergent boundaries?
Mid-ocean ridges and rift valleys — magma fills gap
9
Why does seafloor spreading occur?
Rising magma cools — forms new crust
10
How do plates move at convergent boundaries?
They collide — density difference causes subduction
11
What is subduction?
One plate sinks — denser plate moves downward
12
What forms at oceanic-continental convergence?
Coastal volcanoes — melting plate creates magma
13
What forms at continental-continental convergence?
Large mountains — crust buckles upward
14
What forms at oceanic-oceanic convergence?
Island arcs — magma rises from subducted crust
15
How do plates move at transform boundaries?
Slide horizontally — rough edges lock and release
16
What causes earthquakes?
Stress release — plates suddenly slip
17
What is the Ring of Fire?
Subduction zone band — many volcanoes and quakes
18
What creates hotspot volcanoes?
Rising magma plume — burns through plate
19
Why do plates move?
Convection currents — drag plates along
20
Why does magma melt at subduction zones?
Water lowers melting point — produces magma
21
What do faults represent?
Cracks in crust — movement zones
22
What is a trench and where does it form?
Deep ocean valley — at subduction zones
23
What is soil?
Rock + organic mixture — supports plant growth
24
What is humus?
Decomposed organic matter — holds nutrients and moisture
25
What nutrients are in soil?
Nitrogen, phosphorus, potassium, magnesium, calcium — essential elements
26
Why is soil important for plants?
Provides minerals + structure — enables growth
27
How does soil filter water?
Pores trap contaminants — cleaner water percolates
28
How does soil support nutrient cycling?
Decomposers break biomass — release nutrients
29
What is physical weathering?
Rock broken mechanically — wind, rain, temperature
30
What is chemical weathering?
Rock dissolved by acids — changes mineral makeup
31
What is biological weathering?
Organisms break rock — roots, microbes, animals
32
What is erosion?
Movement of sediment — by wind or water
33
What is parent material?
Original rock source — controls minerals + pH
34
How does climate affect soil formation?
Warm/wet accelerates breakdown — increases soil depth
35
How does topography affect soil?
Steep slopes erode — flat areas accumulate soil
36
How do organisms affect soil formation?
Decomposers create humus — enrich soil
37
What is the O-horizon?
Surface organics — leaves, waste
38
What is the A-horizon?
Topsoil — humus + minerals; most life
39
What is the B-horizon?
Subsoil — minerals + little organics
40
What is the C-horizon?
Least-weathered rock — parent material
41
What is soil degradation?
Loss of fertility — erosion + nutrient loss
42
What causes topsoil loss?
Tilling and erosion — removes nutrient-rich layer
43
What causes soil compaction?
Heavy machinery — reduces pores
44
What causes nutrient depletion?
Repeated farming — removes minerals
45
Why does vegetation prevent erosion?
Roots hold soil — reduce runoff
46
How does desertification occur?
Loss of vegetation — soil dries and erodes
47
Rank soil particles by size.
Sand > silt > clay — large to small
48
What is soil texture?
Ratio of sand, silt, clay — determines behavior
49
Why is loam ideal?
Balanced drainage and retention — best for growth
50
Why does sand drain quickly?
Large connected pores — water flows through
51
Why does clay drain slowly?
Tiny pores — restrict movement
52
What is permeability?
Speed water moves — depends on pore size
53
What is water holding capacity?
Amount retained — depends on pore space
54
How are permeability and water holding related?
Inverse relationship — fast drain means poor retention
55
What increases soil fertility?
Humus, clay, decomposers — store nutrients
56
What decreases soil fertility?
Acids, erosion, over-irrigation — nutrients leach
57
What increases water retention?
Clay + organic matter — slow drainage
58
What decreases water retention?
Sand + compaction — fewer pores
59
How do you test texture?
Settling jar — layers separate
60
How do you test permeability?
Measure drain time — shows pore size
61
How do you test pH?
Indicator strip — measures acidity
62
What does dark soil indicate?
High humus — fertile
63
How do you test nutrients?
Chemical NPK test — detects key ions
64
Why do acidic soils lose nutrients?
Hydrogen ions replace nutrient ions — leaching
65
Why is clay good for nutrient storage?
Negatively charged — binds positive nutrients
66
What gases dominate Earth’s atmosphere?
Nitrogen and oxygen — most abundant
67
Why is nitrogen unreactive in the atmosphere?
Strong triple bond — hard to break
68
Why is oxygen essential?
Supports respiration — releases energy
69
Why is carbon dioxide important?
Greenhouse warming — traps infrared heat
70
Why is water vapor important?
Major greenhouse gas — influences weather
71
What is the exosphere?
Outer layer — fades into space
72
What is the thermosphere?
Very hot layer — absorbs solar radiation
73
Why do auroras occur in the thermosphere?
Charged particles collide — emit light
74
Why does the thermosphere feel cold despite high temperature?
Very few molecules — little heat transfer
75
What is the mesosphere?
Cold middle layer — low density
76
Why do meteors burn in the mesosphere?
Air friction — creates heat
77
What is the stratosphere?
Layer above troposphere — contains ozone
78
Why does the stratosphere warm with altitude?
Ozone absorbs UV — heats layer
79
Why is stratospheric ozone important?
Blocks UV radiation — protects life
80
What is the troposphere?
Lowest layer — weather + densest gases
81
Why does temperature decrease in the troposphere?
Farther from Earth’s warmth — air expands and cools
82
Why does atmospheric pressure decrease with height?
Less air above — lower weight
83
What is a temperature inversion?
Warm air traps cool air — holds pollution
84
What is the greenhouse effect?
Gases trap heat — warms Earth
85
What greenhouse gases exist naturally?
Carbon dioxide, methane, water vapor — heat retention
86
Why do clouds cool the surface during the day?
Reflect sunlight — lower heating
87
Why do clouds warm the surface at night?
Trap heat — reduce cooling
88
Why does warm air rise?
Less dense — expands
89
Why does rising air cool?
Expansion reduces temperature
90
Why does sinking air warm?
Compression increases temperature
91
What creates low pressure at the equator?
Rising warm air — reduces surface pressure
92
What creates high pressure at 30° latitude?
Sinking dry air — warms and dries
93
Why is the equator rainy?
Warm moist air rises — condenses
94
Why are 30° latitudes dry?
Sinking air — little moisture
95
What is the Intertropical Convergence Zone (ITCZ)?
Equatorial rising air belt — constant storms
96
Why does the ITCZ shift seasonally?
Follows direct sunlight — warmest latitudes
97
Why are doldrums calm?
Weak surface winds — mostly rising air
98
What are the horse latitudes?
Calm dry 30° zones — sinking air
99
Why does the Coriolis effect occur?
Earth rotates — deflects moving air
100
Why do trade winds blow east → west?
Coriolis bending — equator rotates fastest
101
Why do westerlies blow west → east?
Opposite deflection — mid-latitudes
102
Why do polar easterlies blow east → west?
Cold dense air — strong deflection
103
Why do Hadley cells form?
Intense equator heating — rising and cycling air
104
Why do Ferrel cells form?
Interaction between Hadley + Polar air — mid-latitude circulation
105
Why do Polar cells form?
Cold dense air sinks — moves equatorward
106
What causes jet streams?
Strong temperature gradients — high-speed winds
107
Why do jet streams influence weather?
Steer storm systems — guide air masses
108
Why does warm air hold more moisture?
More molecular space — prevents condensation
109
What is a watershed?
Land draining to one water body — runoff basin
110
What determines watershed boundaries?
Ridges and divides — control flow direction
111
How does vegetation affect watersheds?
Roots increase infiltration — reduce runoff
112
How does slope affect water movement?
Steeper = more runoff — higher erosion
113
How does soil permeability affect runoff?
Permeable soils absorb water — less runoff
114
Why are estuaries productive?
Mixing of nutrients — supports biodiversity
115
What ecosystem services come from estuaries?
Filtration, habitat, storm buffering — essential support
116
What causes eutrophication?
Excess nitrogen and phosphorus — algae growth
117
Major sources of nutrient pollution?
Sewage, animal waste, fertilizers — nutrient overload
118
Why does sediment pollution increase turbidity?
Particles block sunlight — reduce photosynthesis
119
What are endocrine disruptors?
Hormone-interfering chemicals — affect organisms
120
How does clearcutting increase erosion?
Loss of roots — soil becomes loose
121
How does clearcutting affect stream temperature?
Less shade — water warms
122
What is insolation?
Incoming solar radiation — heats Earth
123
Why do poles receive less insolation?
Low sun angle — spreads energy
124
Why does sunlight travel farther through the atmosphere at high latitudes?
Shallow angle — longer filtration path
125
Why is the equator warm year-round?
Consistent direct sunlight — minimal variation
126
Why are seasons strongest at higher latitudes?
Greater tilt effect — large sun-angle changes
127
What causes seasons?
Earth’s axial tilt — changes sunlight intensity
128
Why does the tilt not change during orbit?
Axis fixed in space — keeps orientation
129
Why is the Northern Hemisphere hot in June?
Tilted toward sun — more insolation
130
Why are winter days shorter?
Tilt away from sun — fewer daylight hours
131
What is a solstice?
Maximum tilt — extreme sunlight
132
What is an equinox?
Equal daylight — sun above equator
133
What is albedo?
Reflectivity — high albedo reflects energy
134
Why do snow and ice have high albedo?
Bright surfaces — reflect most sunlight
135
Why do oceans and pavement have low albedo?
Dark surfaces — absorb heat
136
What is the urban heat island effect?
Cities hotter — low albedo surfaces
137
Why do oceans moderate temperature?
High heat capacity — slow heating/cooling
138
Why are coastal areas milder?
Ocean regulates temperature — reduces extremes
139
Why does melting ice accelerate warming?
Reveals dark ground — reduces albedo
140
Why do clouds reduce daytime heating?
Reflect sunlight — less reaches surface
141
What mainly determines global climate?
Latitude + insolation — control temperature
142
Why is the equator rainy?
Warm rising air — condensation
143
Why are deserts common at 30°?
Sinking dry air — low humidity
144
Why are poles cold?
Low sun angle — weak sunlight
145
How do mountains create rain shadows?
Air rises/wets windward — sinks/dries leeward
146
What happens on the windward side of mountains?
Air cools and rains — condensation
147
What happens on the leeward side?
Air sinks and warms — dry conditions
148
How do oceans influence climate?
Moderate temperature — add moisture
149
What are gyres?
Large circular currents — driven by wind
150
What is upwelling?
Cold nutrient-rich water rising — supports life
151
What drives thermohaline circulation?
Temperature + salinity — density differences
152
Why does water sink at the poles?
Cold and salty — very dense
153
What happens to trade winds in a normal year?
Strong east → west winds — push warm water
154
What happens off South America in a normal year?
Strong upwelling — high nutrients
155
Where is rainfall highest?
Australia + Southeast Asia — warm water region
156
What happens to trade winds during El Niño?
Weaken or reverse — disrupt flow
157
What happens to upwelling?
Decreases — warm water blocks rising cold water
158
How does El Niño affect South America?
Warmer and wetter — warm water arrives
159
How does El Niño affect Australia?
Drought — warm water shifts away
160
Major environmental impact of El Niño?
Flooding in Americas — increased rainfall
161
What happens to trade winds in La Niña?
Stronger than normal — pushes warm water west
162
What happens to upwelling?
Increases — rich fisheries
163
How does La Niña affect South America?
Cooler and productive — strong upwelling
164
How does La Niña affect Australia?
Warm and very wet — intense rainfall
165
How does La Niña affect hurricanes?
Increases Atlantic storms — stronger winds
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