The Earth’s surface is always changing!

The breakdown of the materials of Earth’s crust into smaller pieces.

 Two forms of weathering:  Mechanical: is a process in which only physical changes occur in rock materials. While there are many types and causes of mechanical weathering, each results in the breakdown of rocks and sediments into smaller pieces. (does not change the composition of the rock)  Chemical: occurs when new substances form due to chemical interactions between rock materials and water, air, or biota.

What evidence of weathering do you see in this picture?

 water can cause great chemical changes in rock over long periods of time.  Turn to pg. 152 in text and read about dissolving by acids….

 Most iron-bearing rocks and sediments will oxidize in the presence of atmospheric oxygen. Rust, or iron oxide, is a product of chemical weathering with which most students are familiar. When any element reacts with oxygen, a new substance called an oxide forms.

What evidence of weathering do you see in this picture? Why wasn’t this mass of land weathered away?

Describe how ice causes weathering?

 The rate at which a particular rock weathers depends its environment and its chemical makeup. Environmental conditions such as frequent temperature changes and high rates of precipitation can speed up the weathering process. Rocks that are made up of mostly minerals that are resistant to both chemical and mechanical weathering, such as quartz, will weather much more slowly than rocks that are made up of mostly softer and more chemically reactive minerals, such as feldspar minerals.

 How does weathering break down or change rock?  Weathering breaks down rock into smaller pieces and can also change its chemical makeup.  What is the result of a rock undergoing mechanical weathering?  Mechanical weathering will break a rock apart, increasing its surface area. Smaller rocks, sand, and clay can result from weathering.

 Why is the surface area of a rock important?  The amount of surface area affects the rate at which a rock will weather.  How does chemical weathering differ from mechanical weathering?  Mechanical weathering breaks rock into smaller pieces. The type of rock does not change. Chemical weathering causes changes in the chemical makeup of the rock.

 How can pollutants create acid rain?  Certain chemical pollutants released into the atmosphere dissolve in rain droplets, forming acids.  How does chemical weathering change rock?  Chemical weathering changes the composition of the rock. Chemical weathering can occur as a result of exposure to water, acid, or air.

 Why is weathering slower in cold, dry places?  Rate of weathering depends on temperature and moisture. Cold, dry places have little water to act as a weathering agent and do not have the temperature changes that promote quick mechanical weathering.

 Soil is made up of living and nonliving material spread as a very thin layer over the entire surface of the planet we call earth.  Soil must provide nutrients, water, and air and helps to support the plant.  Soil can be thought of as a mini ecosystem, complete with water, air, microorganisms, worms, burrowing animals, plants, and rock materials.

 organic substances are those that are associated with living things and contain compounds of the element carbon.  Inorganic components of soil are any elements that were not once part of living organisms. They include sediments, water, and air. The sizes of sediments and the amount of pore space within a soil help determine important physical properties of soil.

 Five important factors in the formation of soil are parent material, climate, topography, biota, and time.

 1. Parent Material: the rock or sediment that weathers to form soil.  2. Climate: A region's climate can be described by its average annual precipitation and its average seasonal temperatures. The climate in which a soil forms impacts its characteristics and the rate at which rocks undergo chemical weathering to form soil.

 3. Topography: Topography greatly influences how soils form. In flat landscapes, soil is not eroded or transported as it is in steeply sloped landscapes.  4. & 5. Biota/Time: The action of various living organisms—including bacteria, plants, worms, and burrowing animals—helps speed weathering and the decomposition of organic matter. Soil formation is a constant, slow process. It can take many thousands of years for a mature soil to form as a result of weathering and decomposition.

 Soil is a combination of materials. One part of soil is rock that has been broken down over time by wind, water, and chemical processes.

 Many mature soils consist of three layers, called horizons. The A-horizon is the topmost layer and contains most of a soil's organic matter—often referred to as humus. The B- horizon has less organic matter and more clay minerals that leach downward due to the action of water infiltrating the soil. The C-horizon is the lowest layer and blends into the bedrock. It often contains larger fragments of bedrock that are still undergoing chemical weathering.

 Some properties of soils can be observed by using senses while other soil properties are measured using laboratory techniques. Properties that can be observed with the senses include color, structure, and consistency. Laboratory techniques are used to measure infiltration, soil moisture, pH, fertility, and temperature. Some properties can be both observed and measured, such as texture.

SSoil depth -room for roots to grow AAvailability of water DDrainage- reduce flooding ppH MMinerals OOrganic matter

 Preserving a soil's fertility is a major part of soil conservation. Nutrients in soil can take many lifetimes to develop, but they can be depleted by poor farming practices in only a few years. Farmers use techniques such as crop rotation to preserve soil fertility. Legume crops such as peas, beans, or lentils actually enhance soil fertility. Bacteria that grow on the roots of these crops convert atmospheric nitrogen into a form that can be used by plants. Use the questions below to assess understanding of relationships between soil properties and life.

 Different types of soils form in different locations. Factors that control this distribution include differences in local climate and latitude, rock types, topography, and biota.  Turn to page 164 and look at the map. Note the legend at the left.

 What is the role of parent material in creating soil?  Parent material is the starting material of soil.  Why do soils form rapidly in warm, moist climates?  Rocks are subjected to faster rates of chemical weathering due to warm temperatures and chemical reactions with water.

 How do biota aid in soil formation?  Some organisms create passages for air and water to move into the soil, which speeds up weathering, and others aid in the decomposition of organic matter.  What are soil horizons?  Soil horizons are layers that form as soils mature. Each layer has certain characteristics based upon its age, its position, organic content and moisture movement through it.

 List soil properties that can be observed and measured.  Properties that can be observed include color, texture, structure, and consistency. Properties that can be measured include texture infiltration, soil moisture, pH, fertility, and temperature.  How are soil nutrients related to life?  Plants are the food source for most living organisms, and plants depend on nutrients that they obtain from soils. If soils do not provide adequate nutrients, farmers have to add them to the soil before planting crops.

 Are soils the same everywhere? Why?  Soils vary from place to place because of the effects of parent material, climate, biota, and topography.