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Talus Slopes: Formation and Features — Reading Comprehension

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MS-ESS2-1
MS-ESS2-2
RST.6-8.4

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This earth science passage explains talus slope formation through mechanical weathering processes, aligning with NGSS MS-ESS2-1 (rock transformations) and MS-ESS2-2 (surface processes). It describes freeze-thaw cycles, gravity-driven rockfall, and characteristic 30-40° slopes with angular fragments. Real-world examples include Grand Teton National Park and planetary geology on Mars. The text meets CCSS.ELA-LITERACY.RST.6-8.4 for technical vocabulary like 'mechanical weathering' and supports curriculum standards about erosion hazards and mountain evolution.

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"Static Peak Divide Trail B" by S. Zenner / Wikimedia Commons.

Talus Slopes: Formation and Features

Talus slopes, also called scree slopes, are piles of broken rock fragments that accumulate at the base of cliffs or steep mountainsides. They form through mechanical weathering and gravity-driven erosion, creating distinctive cone-shaped deposits.

Formation Process

● Freeze-Thaw Weathering – Water seeps into cracks in rocks, freezes (expanding by 9%), and splits the rock apart over time.

● Rockfall – Broken fragments tumble downslope due to gravity, often triggered by earthquakes, rain, or frost action.

● Accumulation – Angular rocks collect at the base, forming a steep, unstable slope (typically 30–40° angle).

Characteristics

● Rock Type – Fragments are sharp and angular (not rounded like river rocks).

● Size Variation – Ranges from pebbles to massive boulders.

● Movement – Constantly shifting as new rocks fall and settle.

Examples

● Grand Teton National Park (Wyoming, USA. – Dramatic talus slopes below rugged peaks.

● Dolomites (Italian Alps) – Extensive scree fields from limestone weathering.

● Mars (Planetary Geology) – Satellite images show talus-like features on Martian cliffs.

Talus slopes provide habitats for specialized plants and animals but can be hazardous due to unstable footing. Geologists study them to understand erosion rates and mountain evolution.

Fun Fact: The world's largest documented talus slope is at Mount Olympus in Greece, with rocks that have been continuously accumulating for over 400,000 years! Some of these ancient slopes are so stable that trees have grown on them despite the seemingly unstable rock piles, with root systems that actually help hold the talus in place

What primarily causes talus slope formation?

Volcanic eruptionsWind erosionFreeze-thaw weathering and gravityOcean waves

Why are talus rocks typically angular?

They’ve been smoothed by riversThey break from cliffs without transportThey form from lava coolingAnimals reshape them

What angle do most talus slopes maintain?

5–10°30–40°60–70°Nearly vertical

Which event would NOT trigger rockfall?

Heavy rainEarthquakeGlacier meltingSunny day

Where is a famous talus slope located?

Sahara DesertGrand Teton National ParkMississippi DeltaGreat Barrier Reef

How does talus benefit ecosystems?

Provides stable farmlandCreates habitats for specialized speciesForms permanent lakesPrevents all erosion