--- title: "Erosional and depositional features of river and glacier" subject: "Engineering Geology I" chapter: 6 key: "semester_3/engineering_geology_i:erosional-and-depositional-features-of" source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/erosional-and-depositional-features-of site: BCT Engineering --- # Erosional and depositional features of river and glacier Engineering Geology I · Chapter 6: Physical Geology - Asked in: 2078 Kartik, 4 marks; 2074 Asoj, 5 marks (asked 2 times) - Video: [Glacial Processes and Landforms](https://www.youtube.com/watch?v=CyDRJADPu6U) — Mr Gedge's Geography Channel - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/erosional-and-depositional-features-of - Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-6 ## Question Describe the erosional and depositional features of river and glacier. ## Short answer River erosion forms V-shaped valleys, gorges, waterfalls, potholes and meanders, while deposition builds alluvial fans, floodplains, levees, point bars and deltas. Glacial erosion creates cirques, arêtes, horns, U-shaped valleys and hanging valleys; deposition leaves moraines, drumlins, eskers, erratics and outwash plains. ## Answer #### River **Erosional:** V-shaped valleys, gorges, waterfalls and rapids, potholes, meanders, river terraces. **Depositional:** alluvial fans, floodplains, levees, point bars, braid bars, ox-bow lakes, deltas. **Erosional work** of a river is done by hydraulic action, abrasion, attrition and solution. Features: - **V-shaped valley:** formed by vertical (downward) cutting in the youth stage, in the hills. - **Gorge and canyon:** deep, narrow valley in hard rock, e.g. the Kali Gandaki gorge. - **Waterfall and rapids:** form where hard rock lies over soft rock; a plunge pool forms at the base. - **Potholes:** circular holes drilled in the bed by swirling pebbles. - **River terraces:** step-like old floodplain levels left after the river cuts down again. - **Meanders and ox-bow lakes:** formed by lateral (side) cutting in the old stage. - **Interlocking spurs:** ridges of the valley sides that project alternately into the winding valley of a young river. **Depositional work** occurs when the velocity and carrying capacity fall (on gentle slopes, at the river mouth, and on the floodplain during floods). Features: - **Alluvial fan:** cone-shaped deposit where a mountain stream meets a plain, e.g. the Bhabar zone at the foot of the Siwaliks. - **Floodplain:** broad, flat valley floor built by flood deposits. - **Natural levees:** low ridges of sand and coarse silt built along the banks during floods. - **Braid bars and point bars:** sand and gravel bars in the channel (braid bars) and on the inner bank of bends (point bars). - **Delta:** fan-shaped deposit at the river mouth, e.g. the Ganges-Brahmaputra delta. - **Ox-bow lake and meander scars:** cut-off bends. #### Glacier **Erosional features** - **Cirque (corrie):** armchair-shaped hollow at the head of a glacier, made by plucking and abrasion; a lake in it is a *tarn*. - **Arête:** knife-edge ridge between two cirques. - **Horn (pyramidal peak):** sharp peak left when cirques cut back on all sides, e.g. the Matterhorn. - **U-shaped valley (glacial trough):** the glacier widens and deepens a river valley. - **Hanging valley:** side valley left high above the main trough; it often ends in a waterfall. - **Fjord:** glacial trough drowned by the sea. - **Roche moutonnée, striations and grooves:** smoothed and scratched bedrock surfaces. - **Rock basins and tarns.** **Depositional features.** Material deposited directly by the ice is called **till** (unsorted, unstratified clay, sand, pebbles and boulders); material laid down by meltwater is sorted and layered. Features: - **Moraines:** lateral, medial, terminal (end) and ground moraines. - **Erratics:** large boulders carried far from their source rock. - **Drumlins:** smooth, elongated hills of till, shaped like an inverted spoon. - **Eskers:** long, winding ridges of sand and gravel left by streams under the ice. - **Kames and outwash plains:** mounds and flat areas of sorted sand and gravel built by meltwater. - **Kettle holes:** depressions left where buried ice blocks melted. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How does a waterfall form? A. Cementation of sand B. Lava flow C. Wind erosion D. Hard rock lying over soft rock, with a plunge pool at the base Answer: D. Soft rock erodes faster, undercutting the hard cap. (Key point: Waterfall) 2. What are natural levees? A. Low ridges of coarse silt built along banks during floods B. Fan-shaped deposits at river mouths C. Step-like terraces D. Cut-off lakes Answer: A. Flood water drops coarse load next to the channel. (Key point: Levee) 3. Where does an alluvial fan form? A. In a glacial trough B. Where a mountain stream meets a plain C. At a cave roof D. In a desert only Answer: B. Velocity falls at the slope break, e.g. Bhabar zone. (Key point: Alluvial fan) 4. Which feature is a bowl-shaped hollow at the head of a glacier? A. Esker B. Drumlin C. Cirque D. Kame Answer: C. A lake in it is a tarn. (Key point: Glacier forms) 5. What are moraines? A. Sorted meltwater plains B. Polished rock C. Dunes D. Ridges of till: lateral, medial, terminal and ground Answer: D. They are glacial depositional features. (Key point: Moraine) ## Related in Engineering Geology I - [Erosional features of glacier and underground water](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aerosional-features-of-glacier-and) — Engineering Geology I, chapter 6 - [Erosional and depositional landforms of glaciers](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aerosional-and-depositional-landforms-of) — Engineering Geology I, chapter 6, asked 3× - [Erosional features of underground water](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aerosional-features-of-underground-water) — Engineering Geology I, chapter 6 - [River features; hydrological cycle, aquifer](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Ariver-features-hydrological-cycle-aquifer) — Engineering Geology I, chapter 6