The Earths Surface AKA Rocks and More Rocks

The Earth’s Surface AKA Rocks, and More Rocks

What is a Rock?

What is a Rock? • A rock is a naturally formed solid that is usually made up of one or more types of minerals • A mineral is a substance that: – Forms in nature – Is a solid – Has a definite chemical makeup – Has a crystal structure

True or False? • Rocks are solid, and therefore, never change False! Rocks do change, but the changes usually occur over a huge span of time – thousands to millions of years!

Rock Cycle • The rock cycle is a set of natural processes that form, change, break down, and re-form rocks • Rocks do not need to move through the rock cycle in any particular order • At any point in the cycle, rocks can change in two or three different ways

Rock Cycle • Notice how each rock can change in at least two different ways

Three Types of Rocks • Igneous Rock – Forms when molten (hot liquid) rock cools and becomes solid – Can form within Earth or on the Earth’s surface – Example: granite

Two Types of Igneous Rock • Intrusive Igneous Rock – forms when magma cools within the Earth • Extrusive Igneous Rock – forms when lava cools on the Earth’s surface

Igneous Rocks • Form long lasting landforms because they are harder than other types of rock • Mineral size in igneous rock is determined by the cooling rate of the magma

Three Types of Rocks • Sedimentary Rock – Forms when pieces of older rocks, plants, and other loose materials get pressed or cemented together – Usually contains visible layers – Examples: shale, limestone

Sedimentary Rocks • Rocks can form from plants or shells – Coal – formed millions of years ago from dead plants; many fossils are found in coal – Limestone – formed from shells and skeletons of ocean organisms; these settle to the ocean floor, are buried, and become cemented together as limestone

Sedimentary Rocks • Sediment – material that settles out of water or air • Can be made from small or large particles – Small particles – formed by pressure alone – Large particles – minerals form; act as cement

Three Types of Rocks • Metamorphic Rock – Forms when heat or pressure causes older rocks to change in structure, texture, or mineral composition – Example: marble

Metamorphic Rock • Change from pressure and temperature – Pressure causes rocks to flatten – If the rock melts, it becomes an igneous rock Sedimentary Metamorphic Sandstone Quartzite Metamorphic Igneous Gneiss Dacite

Metamorphic Rock • Recrystallization – heat and pressure break apart minerals; minerals then form new chemical bonds – Crystals can then grow larger – New minerals can form in place of the old ones

Metamorphic Rock • Can be separated into two categories: – Foliated Rock – develop when rocks are under pressure; foliation – the arrangement of minerals in flat or wavy parallel bands – Non-foliated Rock – rocks are not exposed to high pressure; example: marble – used by sculptors because it doesn’t split into layers