Grade 7
The Human Knowledge Project
Unit 8 — Earth Systems, Weather, Climate, and Plate Tectonics
Welcome back!
Earth is a dynamic planet that is constantly changing.
Powerful forces inside and outside the Earth shape mountains, oceans, rivers, coastlines, and even the atmosphere above us.
Scientists study these systems to better understand natural hazards, weather, climate, and the processes that make Earth a suitable home for life.
Today you will investigate Earth's structure, plate tectonics, weather, climate, and the interactions between Earth's major systems.
Earth's Four Major Systems
Earth can be divided into four interconnected systems.
These include:
- geosphere
- hydrosphere
- atmosphere
- biosphere
Each system influences the others.
Changes in one system often produce changes throughout the entire planet.
Layers of the Earth
Scientists divide Earth's interior into several layers.
These include:
- crust
- mantle
- outer core
- inner core
The crust is Earth's thin outer layer.
The mantle consists of hot rock that slowly flows over long periods of time.
The outer core contains liquid iron and nickel.
The inner core is solid because of the immense pressure.
Plate Tectonics
Earth's crust is broken into large sections called tectonic plates.
These plates move slowly across the surface.
Their movement produces:
- earthquakes
- volcanoes
- mountain ranges
- ocean trenches
Plate tectonics explains many of Earth's largest geological features.
Earthquakes
An earthquake occurs when energy is suddenly released as tectonic plates move.
Earthquakes may cause:
- ground shaking
- landslides
- tsunamis
- structural damage
Scientists use seismographs to detect and measure earthquakes.
Communities prepare for earthquakes through emergency planning and safe building practices.
Volcanoes
A volcano forms when molten rock rises to Earth's surface.
Volcanic eruptions release:
- lava
- ash
- gases
Although eruptions can be destructive, volcanic materials also create fertile soils and new landforms.
Weather
Weather describes atmospheric conditions over a short period of time.
Weather includes:
- temperature
- precipitation
- humidity
- wind
- cloud cover
- air pressure
Meteorologists use observations, satellites, and computer models to forecast weather.
Climate
Climate describes the average weather conditions of a region over many years.
Climate depends on factors such as:
- latitude
- elevation
- proximity to oceans
- prevailing winds
- ocean currents
Weather changes daily.
Climate changes much more slowly.
The Water Cycle
Water continually moves through Earth's systems.
Major processes include:
- evaporation
- condensation
- precipitation
- runoff
- infiltration
- transpiration
The water cycle supplies fresh water to ecosystems around the world.
Human Impact
Human activities influence Earth's systems.
Examples include:
- air pollution
- water pollution
- deforestation
- urban development
- conservation
- renewable energy
- resource management
Scientists study these impacts to better understand how to protect Earth's environment.
Activity
Complete the following:
- label Earth's layers
- identify major tectonic plate boundaries on a world map
- explain how earthquakes occur
- compare weather and climate
- diagram the water cycle
- research one major volcanic eruption or earthquake and summarize its effects
Practice
Answer these questions.
What are Earth's four major systems?
What are the layers of Earth?
What causes earthquakes?
How do volcanoes form?
What is the difference between weather and climate?
Why is the water cycle important?
Review
Today you learned:
- Earth is composed of interconnected systems
- Earth's interior contains several distinct layers
- tectonic plates continually reshape the planet
- earthquakes and volcanoes result from plate movement
- weather and climate describe different atmospheric conditions
- the water cycle continually recycles Earth's water
- people both affect and depend upon Earth's natural systems
Understanding Earth systems helps us prepare for natural hazards, manage resources wisely, and better understand the planet we call home.
Looking Ahead
Next we will begin Grade 7 World History by examining the rise of the classical civilizations, their governments, cultures, scientific achievements, and the ways they influenced later societies.