Identify water, landforms and evidence of surface change

Learning goal: Identify Earth's major surface features, locate freshwater and connect landforms with processes that shape them. Looking at Earth from space reveals broad water-covered regions and land. About seven tenths of the surface is covered by water. USGS gives the more precise estimate of about seventy-one percent. Surface coverage describes area; it does not describe the fraction of all water that is fresh.

Most of Earth's water is in the salty ocean. Freshwater is a small share of all water and occurs in lakes, rivers, underground spaces and glaciers, among other places. Groundwater occupies spaces and cracks in soil and rock; it is not all one giant underground lake. A glacier stores frozen freshwater. A spring is a place where groundwater flows naturally out at the surface. Freshwater does not automatically mean safe drinking water.

Landforms have recognizable shapes and relationships. A hill is a raised area, and a mountain rises prominently above surrounding land. A mountain range is a group of connected mountains. A valley is a lower area between higher slopes. A canyon is a deep valley with steep sides. A plain is a broad area with relatively little change in elevation. Identify features by their shape and setting, not just by the color used on a map.

Moving water shapes other features. A stream follows a channel, often through a valley. A floodplain is relatively flat land beside a river that can be covered during flooding. A delta can build where a river delivers sediment into a lake or sea and deposits it near its mouth. Not every river mouth makes the same-shaped delta; water movement and available sediment affect the result.

Other features reflect different processes. Wind can deposit sand into dunes. A volcano can build a raised landform as erupted material accumulates. An island is land surrounded by water; some islands are volcanic, but not all form that way. Moving glaciers can scrape surfaces and leave ridges or other deposits of sediment. A cave is an underground opening, and a sinkhole is a surface depression that may form where material dissolves or an underground space collapses.

A topographic map represents elevation, or height relative to a reference level. Contour lines connect places of equal elevation. In the fictional map, nested contours are labeled one hundred, one hundred twenty and one hundred forty meters. Moving inward across those increasing values goes uphill. Closer contour spacing indicates a steeper slope when the contour interval is consistent. A relief model uses raised material to show the same height relationships in three dimensions.

Landforms change on different time scales. A river can gradually cut a valley and deposit sediment elsewhere. A flood can quickly move large amounts of sediment. An earthquake can shift ground or trigger a landslide. A volcanic eruption can rapidly add new material. A dramatic event can destroy one surface feature while building another; change does not always mean only loss.

Use evidence from maps, photographs and supervised field observations to connect shape and process. A single picture shows a surface at one time. A dated before-and-after pair from the same viewpoint can show a change, but deciding its cause may require rainfall records, event reports or other observations. Do not call every hollow a sinkhole or every raised feature a volcano without supporting evidence.

Worked map reading: A trail starts on a contour labeled one hundred meters and ends on one labeled one hundred forty. Its net elevation gain is forty meters. That is vertical height change, not trail length. A route that crosses fewer closely packed contours may be gentler, but distance and other obstacles also matter.

Worked feature explanation: A river enters a lake and a new patch of sediment is visible near the mouth in later photographs. Deposition is a supported explanation for the accumulating material. Additional observations would be needed to establish the rate or to predict the patch's future shape.

Guided performance: Make a clay hill and draw several equal-height contour levels on a plan view. Match the raised model to the flat map. Then use a globe and source-identified landform photographs to identify mountains, valleys, floodplains, deltas, dunes and glacial features. Explain the evidence used for each identification.

Independent evidence: Produce a labeled map or relief model with a key and an explanation of two shaping processes. Locate ocean water and several freshwater stores, keeping water amount separate from surface coverage. Compare a dated image pair and distinguish the observed change from the proposed cause. Record source titles and dates rather than presenting a fictional model as a map of an actual Ohio place.