Rock Assessment D. Crowley, 2008

Rock Assessment To understand the process of rock weathering Monday, July 23, 2018 To understand the process of rock weathering

Why do rocks break down? Task: the following passage about rocks has lots of mistakes in it Your task is to read the passage carefully and identify all the mistakes in it You need to re-write the passage in your book and correct the mistakes. Whatever words you correct you must underline! This assessment will identify your knowledge of both rocks and the weathering process…

Section 1 There are two different types of rock. These are itneous and metamorphic. All the types of rocks are made up from grains that fit together. These grains are made from different chemical compounds called vitamins. The way that the grains in rocks fit together affects the texture. If the grains are close together with no gaps they are said to be porous. If the grains are more rounded with gaps between them they are called interlocking. Interlocking grains are sometimes called crystals.

Section 2 Sandstone has rounded grains. Sandstone is porous because water cannot get into the gaps between the grains Draw an interlocking rock structure Limestone has interlocking grains. The interlocking grains are sometimes called crystals. This rock is porous Draw a porous rock structure

Section 3 Rocks can be worn away. This is called breaking down. There are three main ways rocks can be broken down: these are chemical weathering, physical weathering and human weathering. Chemical weathering happens when rainwater becomes slightly alkaline. The gases that cause this are sulphur oxides and potassium oxides. Physical weathering can happen via cold-melt action when rain water seeps into cracks in the rocks. If the temperature rises above freezing the water turns to ice and expansion pushes the rock apart. This keeps happening each time the water thaws and refreezes. Eventually bits of rock break off.

Section 4 Heat energy from the sun results in rock contraction. When conditions become colder the rock contracts. Over time this continued expansion and contraction can cause rocks to become malleable, and pieces break off. Biological weathering is where rocks are broken up by aliens and fish. An example of this is when a spaceship lands on a rock and crushes it.

Levels Level 4 – obvious mistakes are picked up, but not corrected Level 5 – obvious mistakes are picked up, and corrected Level 6 – most of the mistakes are picked out, but not all are corrected Level 7 – majority of mistakes are picked out and corrected

Answers Section 1 There are three different types of rock. These are igneous, sedimentary and metamorphic. All the types of rocks are made up from grains that fit together. These grains are made from different chemical compounds called minerals. The way that the grains in rocks fit together affects the texture. If the grains are close together with no gaps they are said to be interlocking. If the grains are more rounded with gaps between them they are called porous. Interlocking grains are sometimes called crystals.

Answers Section 2 Sandstone has rounded grains. Sandstone is porous because water can get into the gaps between the grains Draw an interlocking rock structure Granite has interlocking grains. The interlocking grains are sometimes called crystals. This rock is interlocking Draw a porous rock structure

Answers Section 3 Rocks can be worn away. This is called weathered / eroded. There are three main ways rocks can be broken down: these are chemical weathering, physical weathering and biological weathering. Chemical weathering happens when rainwater becomes slightly acidic. The gases that cause this are sulphur dioxide and nitrogen oxides. Physical weathering can happen via freeze-thaw action when rain water seeps into cracks in the rocks. If the temperature drops below freezing the water turns to ice and expansion pushes the rock apart. This keeps happening each time the water thaws and refreezes. Eventually bits of rock break off.

Answers Section 4 Heat energy from the sun results in rock expansion. When conditions become colder the rock contracts. Over time this continued expansion and contraction can cause rocks to become brittle, and pieces break off. Biological weathering is where rocks are broken up by plant and animal activity, e.g. plant roots extend their roots through cracks in rocks as they grow.