Earth & Space Science · Seasons, Water & Deep Time

Detroit's seasons, lakes, and salt mine all come from Earth's systems.

Sitting at 42°N beside the Great Lakes, Detroit is a front-row seat for how sunlight, water, and rock shape a place. This unit covers Earth's tilt and orbit, the water cycle and regional climate, and the geology under the city — including salt that formed more than 400 million years ago.

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NGSS Standards Addressed High School

  • HS-ESS1-4 Use mathematical or computational representations to predict the motion of orbiting objects in the solar system.
  • HS-ESS2-2 Analyze geoscience data to make the claim that one change to Earth's surface can create feedbacks that cause changes to other Earth systems.
  • HS-ESS2-4 Use a model to describe how variations in the flow of energy into and out of Earth's systems result in changes in climate.
  • HS-ESS2-5 Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes.

NGSS Standards Addressed Middle School

  • MS-ESS1-1 Develop and use a model of the Earth-sun-moon system to describe the cyclic patterns of lunar phases, eclipses, and seasons.
  • MS-ESS2-1 Develop a model to describe the cycling of Earth's materials and the flow of energy that drives this process.
  • MS-ESS2-4 Develop a model to describe the cycling of water through Earth's systems driven by energy from the sun and the force of gravity.
  • MS-ESS2-6 Develop and use a model to describe how unequal heating and rotation of Earth cause patterns of atmospheric and oceanic circulation that determine regional climates.
Warm-Up

Bell-Ringers

Project one at the start of class. Each has a click-to-reveal discussion note. Try Project Mode for full-screen slides. More formats (Notice and Wonder, CER, Fact or Fiction, and more) are in the Bell-Ringer Bank.

Energy

Detroit is at about 42°N. Using altitude = 90° − latitude + declination, find the Sun's noon altitude on the summer solstice (declination +23.4°) and the winter solstice (−23.4°). How does that change the solar energy reaching each square meter of ground?

Discussion notes
Summer: 90 − 42.3 + 23.4 = 71.1°. Winter: 90 − 42.3 − 23.4 = 24.3°. A beam striking at a low angle spreads over a larger area (area ∝ 1 / sin θ), so each square meter gets about 2.3 times less energy in winter (sin 71.1° ÷ sin 24.3° ≈ 2.3), before counting the shorter winter days.
Water

Why are cities near the Great Lakes, like Detroit, generally milder in winter and cooler in summer than inland places at the same latitude?

Discussion notes
Water has a high specific heat, so large lakes warm and cool slowly. In summer the lakes stay cooler than the land and cool nearby air; in fall and winter they release stored heat and moderate cold. This is the idea of thermal inertia, and it helps explain regional climate (HS-ESS2-4).
Transportation

Rock salt used on Detroit roads is mined from a deposit beneath the city that formed when an ancient sea evaporated. What conditions must have existed when it formed?

Discussion notes
A warm, dry climate where evaporation exceeded water inflow, and a shallow, partly isolated basin that kept refilling with seawater. Repeated cycles of flooding and evaporation left thick layers of salt (an evaporite).
Energy

Earth is slightly closer to the Sun in early January than in July. So why is Detroit coldest in January?

Discussion notes
Seasons are caused by Earth's 23.5° axial tilt, not by distance. In January Detroit's hemisphere tilts away from the Sun, so sunlight arrives at a low angle and days are short.
Water

A raindrop falls on Detroit. Describe one path it could have taken after leaving Lake Erie as water vapor.

Discussion notes
Sunlight evaporates lake water into vapor, the vapor rises and cools, condenses into cloud droplets, winds carry the cloud over Detroit, and the water falls as precipitation. This is the water cycle.
Transportation

Road salt is mined as rock salt. Is it an igneous, sedimentary, or metamorphic rock? How do you know?

Discussion notes
Sedimentary. It formed from salt crystals left behind when an ancient sea evaporated and built up in layers over time.
Hands-On

Labs

Seasons Over Detroit: Sun Angle & Heating

50 minPairsEnergy and the seasons

Students shine a lamp on black paper at three angles to measure how light angle changes heating, then calculate the Sun's noon altitude for Detroit on the equinox and both solstices.

Download LabTeacher key

Michigan's Salt Beds: Growing an Evaporite

30 min setup + daily checksSmall groupsRocks and the rock cycle

Students evaporate saturated salt water under fast, medium, and slow conditions and compare crystal size, modeling the origin of the rock salt mined beneath Detroit.

Download LabTeacher key

Great Lakes Water Level Data Dive

40 minPairsWater and climate data (also in Environmental Science)

Students graph 55 years of real Detroit River water levels from NOAA and interpret cycles, ranges, and trends.

Download LabTeacher key
Explore

Simulations

Original on The Lab

Seasons Over Detroit

Move through the year and watch Detroit's noon Sun angle, day length, and relative solar energy change with Earth's tilt.

Launch Simulation →

Gravity and Orbits

PhET Interactive Simulations — explore how gravity governs orbits for the Sun-Earth-Moon system.

Open Simulation →

The Greenhouse Effect

PhET Interactive Simulations — model how atmospheric gases change Earth's energy balance.

Open Simulation →

NOAA Great Lakes Environmental Research Lab

Public data on Great Lakes water levels, ice cover, and temperature from NOAA GLERL.

Open Tool →
Go Further

Project Ideas

Design challenge

Solar Panel Tilt Optimizer

Use the sun-angle formula to find the best fixed tilt for a Detroit rooftop, propose seasonal adjustments, and estimate how much more energy a tilted panel receives than a flat one.

Data project

Great Lakes Ice Cover & Winter Severity

Use public NOAA ice-cover and temperature records to test whether colder winters produce more ice, and present the evidence.

Story map

Underground Detroit

Build a story map of the Michigan Basin, the ancient sea, and the salt mine beneath Detroit, from deposition to road salt.

Field project

Shadow Stick Sun Tracker

Measure the shadow of a meter stick every hour on a sunny day, graph length versus time, and explain the pattern.

Model project

Seasons with a Lamp and Globe

Use a lamp and a tilted globe to model the seasons and explain, with labeled diagrams, why July is warmer than January.

Experiment

Lake Effect Model

Heat a tray of water and a tray of sand under a lamp, then let both cool, and compare how fast each changes temperature.

Assess

Show What You Know: Exit Ticket

Three quick questions to close the lesson. Answers are hidden until you click. Use Project Mode to display them full-screen.

Question 1

Explain why Detroit is warmer in July than in January. Is it because Earth is closer to the Sun in July?

Answer
No. Earth is slightly closer to the Sun in early January. The 23.5° axial tilt makes the Sun higher in the sky and days longer in summer, so energy is more concentrated and delivered for more hours.
Question 2

Why does table salt crystallize when salty water evaporates, and how does that relate to underground salt beds beneath Detroit?

Answer
As water evaporates, dissolved salt becomes more concentrated until it exceeds its solubility and crystallizes. Thick salt layers formed roughly 400 million years ago when an ancient inland sea evaporated.
Question 3

Water has a high specific heat. How does that help explain why cities beside the Great Lakes have milder temperature swings?

Answer
Large water bodies warm and cool slowly. In summer the lakes keep nearby air cooler, and in fall and winter they release stored heat, moderating temperatures.
Question 1

What causes the seasons on Earth?

Answer
Earth's axis is tilted about 23.5°. As Earth orbits the Sun, each hemisphere tilts toward or away from it, changing sunlight angle and day length. Distance from the Sun is not the cause.
Question 2

Describe how water from Lake Erie could end up falling as rain in Detroit.

Answer
Sunlight evaporates lake water into vapor, the vapor rises and condenses into clouds, and the water falls as precipitation. This is the water cycle.
Question 3

Rock salt is mined under Detroit. Is it igneous, sedimentary, or metamorphic? How do you know?

Answer
Sedimentary. It formed when salt crystals deposited as an ancient sea evaporated, building layers over time.

View project rubrics →

Why Does This Matter?

Earth & Space Science, built on Detroit

Energy

Detroit's low winter Sun and high summer Sun determine how much solar energy rooftops can capture and how much sunlight heats homes through windows — direct, practical uses of sun-angle science.

Water

The Great Lakes moderate Detroit's temperature extremes, and their water levels swing through multi-year cycles that affect shoreline infrastructure and shipping.

Transportation

Salt mined beneath Detroit helps keep roads open through winter, a direct link between a 400-million-year-old evaporated sea and daily commuting.

Technology

The National Weather Service's Detroit/Pontiac forecast office and the Michigan Science Center put atmospheric and space science technology within a short trip of local classrooms.

Careers

Who works on this in Detroit?

Real roles and organizations in and around the city where this science is part of the job.

Meteorologist

National Weather Service Detroit/Pontiac office, local TV stations

Analyzes atmospheric data to forecast Detroit's storms, heat waves, and winter weather.

Geologist / geotechnical engineer

Detroit Salt Company, MDOT, engineering firms

Studies rock and soil layers to plan mines, foundations, roads, and tunnels safely.

Great Lakes hydrologist

NOAA Great Lakes Environmental Research Laboratory, University of Michigan

Tracks lake levels, ice cover, and water flow, and models how climate changes the Great Lakes.

Planetarium / science educator

Michigan Science Center

Teaches astronomy and Earth science through shows, exhibits, and hands-on programs.

Space scientist / engineer

University of Michigan and Wayne State University research groups

Builds instruments and analyzes data about the Sun, planets, and Earth's space environment.