Lesson 3: Rocks, Minerals, and Soil

Igneous Rocks

● Rocks form from molten rock, or magma ● Magma heats up below or inside Earth’s crust. Under heat and pressure, it

can break through to Earth’s surface as lava.● When lava or magma cools, igneous rock forms.

Sedimentary Rocks

● Sediment is made of particles when dirt, sand, and fossils when they settle into layers in basins or flat surfaces.

● Overtime, the sediment becomes stuck like glue.● Different types of sedimentary rocks include:

○ Sandstone: ribbons of different sand○ Gray or white limestone: bones and shells og seas creatures.○ Conglomerate: chunks of rock glued together by other rock.

Sandstone

Limestone

Conglomerate

Metamorphic Rock

● Metamorphic rock is formed when particles of other rocks are combined by high pressure and temperature

● It usually develops new crystals.● Example: Marble is made when limestone or chalk is heated and

squeezed.

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Minerals● Rocks are made up of one or minerals● Minerals have properties including color, texture, luster, streak, cleavage,

and hardness. ● Easily observed properties:

○ Luster: How a mineral’s surface reflects light. . Glassy luster is shiny and Metallic luster looks like polished metal. . Luster can be waxy, pearl, chalky, and other lusters.

○ Streak: Color in powdered form.○ Break: Minerals with perfect cleavage break into flat, smooth layers. Other minerals that

break into non flat shapes or splinter.○ Hardness: How easily the surface of a mineral can be scratched.

● Can be sorted into metals (gold and silver) or gems (diamonds)

Soil

● A mixture of rock particles, air, water, and decomposing matter.● Main rock particles in soil are sand, silt, and clay.● The type of rock particles in soil affect how it drains (water pours

quicker through sandy soil than clay).● Topsoil occurs when air and organic matter (humus) mix

○ RIch topsoil supports plant growth● Soil profile: A cross section of soil under several layers of soil

types