Agenda: Wed Finish presentations Rock Cycle PPT and notes Pres. marks handed back tomorrow

Rocks and the Rock Cycle!!!

Important Backgrounder… All rocks are made up of 2 or more minerals, but minerals are not made up of rocks Mineral- a naturally occurring, pure, non-living substance found in rock There are about 3000 known minerals on earth

3 Categories of Rock Rocks are made up of a variety of minerals and can be classified into three main categories: Igneous Sedimentary Metamorphic

Agents of Change Weathering-break down of rock into smaller particles Erosion-wearing down of the earth’s surface followed by movement Deposition- the laying down of sediments Compression Heat and Pressure- metamorphism Melting Cooling

Magma/Lava Melted or molten rock If it is under ground, it is called Magma If it is above ground, it is called Lava

Igneous Rock Ignis= fire in Latin Formed from the cooling and hardening (solidifying) of hot melted magma that rises from deep under the earth’s crust then cools and hardens

Igneous Can be either intrusive or extrusive Intrusive: form below the earth’s surface, crystals in the rock are usually larger because they cool more slowly Extrusive: form on the earth’s surface as a result of volcanic activity, crystals are usually smaller because lava cools very quickly

Characteristics: glass-like or sponge-like depending on how close it is to the surface.

Intrusive Igneous Rock Large crystals cooled slowly below the surface

Example 1: Granite

Extrusive Igneous Rock Small Crystals if cooled quickly on the earths surface

Example 2: Basalt Small crystal rock, usually dark in colour

Example 3: Pumice Sponge like

Sedimentary Rocks Sediments are small pieces of rock that have been broken down by wind/water/etc. Formed by compression (gluing together) of sediments over millions of years

Sedimentary Rocks Sedimentary rocks can be classified in two ways: Clastic: made from the “gluing” together of sediments (small pieces of rock) over time Non-Clastic: made from remains of plants and animals

Sedimentary Rocks Sedimentary rocks typically form in layers and can easily break

Example 1: Sandstone Formed by sand sediments Gritty feeling

Example 2: Shale Clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments

Example 3: Limestone Sedimentary rock

Metamorphic Rocks Formed when pre-existing rock is transformed (changed) under tremendous heat and pressure This occurs when layers of rock below the earth’s surface experience heat and pressure due to the overlying material

Characteristics: hard, dense, less porous, have crystals in non-parallel layers This takes millions of years to occur

Example 1: Gneiss Formed from granite (igneous rock)

Example 2: Slate Formed from shale (sedimentary rock)

Example 3:Marble Formed from limestone

The Rock Cycle How rocks are formed 1. Start with molten rock known as magma 2. When it cools, this melted rock hardens and turns into igneous rock 3. This rock is weathered (broken up), eroded (worn away), and deposited (collected) 4. The deposited material layer and harden, forming sedimentary rock

5. If igneous or sedimentary rock undergoes pressure or heating, it becomes metamorphic rock

Copy this next diagram down…..this is the Rock Cycle! Be familiar with each step of the process