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Earth Science Notes (9th Grade)
Clear • Detailed • Easy to Understand • High-Value Study Guide
1️⃣ What Is Earth Science?
Earth Science is the study of our planet — how it was formed, how it works, and how it changes over time. Earth Science has four main branches :
- Geology – Study of rocks, minerals, and Earth’s surface
- Meteorology – Study of weather and climate
- Oceanography – Study of oceans
- Astronomy – Study of space and objects beyond Earth
2️⃣ The Structure of the Earth 🌎
Earth has three main layers :
🟤 1. Crust
- Thin outer layer
- Where we live
- Made of solid rock
- Two types: o Continental crust (land) o Oceanic crust (under oceans)
🔴 2. Mantle
- Thickest layer
- Very hot
- Made of semi-solid rock (magma)
🟡 3. Core
- Center of Earth
- Extremely hot (about 5,000–6,000°C)
- Two parts: o Outer core (liquid metal) o Inner core (solid metal) The movement of the liquid outer core creates Earth’s magnetic field.
3️⃣ Minerals and Rocks 🪨
What Is a Mineral?
A mineral is:
- Naturally occurring
- Solid
- Inorganic
- Has a crystal structure
- Has a definite chemical composition Example: Quartz, gold, diamond
5️⃣ Plate Tectonics 🌍
Earth’s crust is broken into large pieces called tectonic plates. These plates move slowly (a few centimeters per year).
Types of Plate Boundaries
➡️ Divergent Boundary
Plates move apart Example: Mid-ocean ridges
⬅️ Convergent Boundary
Plates move toward each other Can cause:
- Mountains
- Volcanoes
- Earthquakes
↔️ Transform Boundary
Plates slide past each other Causes earthquakes Example: San Andreas Fault
6️⃣ Earthquakes 🌋
An earthquake happens when energy is suddenly released in Earth’s crust. Important terms:
- Focus – where the earthquake starts underground
- Epicenter – point on the surface above the focus
- Seismic waves – energy waves from earthquakes Earthquakes are measured using:
- Richter Scale (magnitude)
- Moment Magnitude Scale (Mw) (modern scale)
7️⃣ Volcanoes 🌋
A volcano is an opening in Earth’s crust where magma escapes.
Types of Volcanoes
1. Shield Volcano a. Wide and gently sloping b. Example: Mauna Loa 2. Composite Volcano a. Tall and cone-shaped b. Explosive eruptions c. Example: Mount St. Helens 3. Cinder Cone a. Small and steep
8️⃣ Weather vs Climate ☁️
Weather
Short-term atmospheric conditions Example: Rain today
1️⃣ 1️⃣ Oceans 🌊
Oceans cover about 71% of Earth’s surface. Major Oceans:
- Pacific Ocean
- Atlantic Ocean
- Indian Ocean
- Arctic Ocean
- Southern Ocean Oceans help:
- Control climate
- Provide oxygen
- Support life
1️⃣ 2️⃣ The Solar System ☀️
The Sun is a star at the center of our solar system. Planets in order:
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune Example:
- Mars is known as the Red Planet.
- Jupiter is the largest planet.
1️⃣ 3️⃣ The Moon 🌙
Earth’s Moon:
- Controls ocean tides
- Reflects sunlight
- Has phases (new moon, full moon, etc.) It formed about 4.5 billion years ago.
1️⃣ 4️⃣ Natural Resources 🌱
Natural resources are materials from Earth that humans use.
Renewable Resources
Can be replaced quickly Examples: Sunlight, wind
Nonrenewable Resources
Take millions of years to form Examples: Coal, oil, natural gas
