Kansas Grade 8 Science

Separate ancient chalk formation from later landscape erosion

Use a Kansas Geological Survey source to distinguish ancient marine deposition from later erosion at Monument Rocks, and compare the time and spatial scales of change.

The Kansas science standards directory identifies NGSS adoption in 2013 and review in 2025. It links the disciplinary-core-idea arrangement used here. Use the Kansas-linked NGSS disciplinary-core-idea arrangement for the selected performance expectation and its complete supporting information. NGSS middle-school expectations use a Grades 6–8 band. The activity here is a suggested study focus; consult the school’s plan for its local grade placement.

Did the sea create the present-day pillars in one event?

The Kansas Geological Survey’s 2016 field guide explains that Monument Rocks in Gove County consists of chalk originating from material deposited in a Cretaceous inland sea about 80 million years ago. It also describes later exposure and erosion, with more resistant beds protecting softer chalk below. Students use this source to separate the origin of the material from the shaping of the present landform. This is a suggested Grade 8 study focus within Kansas’s middle-school band, not a required grade-specific assignment.

Explain the evidence or model

A useful explanation has more than one stage. Marine material accumulated over a long interval, was buried, and became rock. Later processes exposed and removed material, leaving resistant remnants. The present pillars therefore are not simply piles placed in their current shape by a single ancient wave. The field guide also records a rapid local change: the Sphinx outlier’s head fell in 1986. That event illustrates how a long landscape history can include a short, concentrated change. Students distinguish the broader history of the chalk from the collapse of part of one feature. Neither observation alone supplies a complete record of every intervening process.

What to check in the explanation

The source’s approximate age concerns ancient deposition; it is not the date when the current pillar shape was completed. A photograph of today’s feature can show its present form, but cannot directly show all past stages or establish an erosion rate without additional dated evidence. The reported collapse date also does not identify every immediate cause. Keep claims tied to what the source documents rather than attribute the event to a particular storm or mechanism without support. Relative resistance helps explain preservation, but it does not mean the softer material stopped changing. A surviving remnant can still undergo erosion.

Plan the next activity

1. Identify which statements concern material origin and which concern later landform change.
2. Compare a broad, long-term process with a rapid change at one feature.
3. Write an explanation that connects each stage to identified source evidence.

Create a two-part explanation: one paragraph on formation and exposure, and another on changing remnants. Cite the field-guide page and label any original sequence diagram as conceptual, not a dated reconstruction. To examine present change, a teacher could provide comparable dated photographs or measured records from an appropriate published source. Do not manufacture a millimeters-per-year value from one picture. The selected Kansas-linked expectation emphasizes explanations at differing time and spatial scales, including local features where appropriate. Monument Rocks gives a Kansas example, while the broader middle-school course also needs other geoscience processes and evidence beyond this single landmark.

Supporting source: Kansas Geological Survey 2016 field guide: PDF page 69 (printed page 65).