Section Nine Earth Science Landforms and Changes to Earth’s Surface

Landforms The surface of Earth is covered with a variety of different types of landforms. valleymountains plain desertisland coastline canyon delta volcano

Changes to Earth’s Surface The surface of Earth is always changing. Changes can be slow or fast. Changes can break down or wear away landforms. Changes can also build up or create new land.

Weathering Weathering is the process by which rocks are broken down into smaller pieces. Weathering is mainly caused by wind, water and ice. Plants, temperature changes, and animals can cause weathering too. Weathering is a slow process and the result of weathering is smoother rocks or rock formations gradually getting smaller.

Erosion and Deposition Erosion is the movement of rocks, soil, and sand to a new place. Erosion is caused by wind, water, ice and gravity. After the Earth materials are moved by erosion, they are dropped in a new spot, which is called deposition.

Land Formed by Erosion and Deposition. As rivers flow, they pick up and carry a great deal of soil, rocks and sand. At the mouth (end) the river will normally slow down, widen, and empty into a larger body of water like a gulf or ocean. When this happens it deposits all of the materials it was carrying. This deposition forms new land called a delta.

Land Changed by Erosion and Deposition. Glaciers are ice masses. They move like a slow flowing river. Underneath a glacier where the ice meets the ground, large amounts of soil and rock are crushed and ground apart. Glaciers transport (move) and deposit the materials beneath them in new places. Glaciers also carve away the land beneath them making valleys.

Formation of Caves A cave is a natural opening usually in rock. Caves form when water seeps into the ground and wears away rock beneath the surface. The water that seeps through can carry minerals that slowly build up and create stalactites from cave ceilings or stalagmites on cave floors.

Tectonic Plate Movement Sections of the Earth called plates float and move on top of the mantle of the Earth. The plates are always moving and sometimes their movements cause earthquakes or volcanoes.

Earthquakes The edges where the plates touch is called a fault. As plates move, they sometimes slide or rub against each other. If they can’t slide easily, pressure will build up in the spots where they touch. When one plate finally pushes past another, the pressure is released and the ground shakes causing an earthquake.

Volcanoes Volcanoes occur mainly in areas where one plate pushes under another. When a volcano erupts, magma (molten rock) pushes its way up to the Earth’s surface. Magma on the Earth’s surface is called lava. Lava will cool and create new land around the volcano’s crater.

Changes to Earth’s Surface Questions

1.Rivers carry a great deal of sediment (rocks, sand, and soil) as they flow. When a river enters a larger body of water it slows and can drop the sediment. What landform is likely to be created from the sediment? A. canyon B. delta C. island D. coast 2.What is most responsible for this sea arch? A. Plate tectonics B. Earthquakes C. Erosion D. Deposition

3.How do plants most commonly break large rocks into smaller pieces? A. Plant leaves conduct heat from the sun which they pass to surrounding rocks. B. Plant roots grow into cracks in rocks. C. Seed from plants fall into rocks and release acids D. Stems of plants surround and squeeze rocks. 4. When volcanoes erupt magma flows out of the crater onto to the Earth’s surface as lava. What is a likely to happen to the Earth’s surface after a volcanic eruption? A. New land is formed when the lava cools and hardens. B. There is no change to the Earth’s surface. C. The land surrounding the volcano will be lower than before. D. The lava will help enrich the soil so the trees and plants grow better..

5.Which of the following can be caused by weathering? A. cracks forming in a boulder B. rocks melting to form magma C. glaciers forming on a mountainside D. pebbles combining to form a large rock

Answers and Explanations 1. B – when a river deposits rocks, soil, and sand as it enters a body of water, the deposited materials will most likely form a delta. 2. C – the waves are most responsible for causing the erosion that wears away the rock in the sea arch 3. B – the most common way that plants break apart rocks happens when the roots of plants grow into cracks in the rocks 4. A – the most likely result of volcanic eruptions is the build up of new land 5. A – weathering is the breaking apart of rocks, and when rocks (like boulders) heat up from the sun shining on them and cool down at night, they can begin to form cracks which can cause them to weather (break apart)