President Eisenhower Memorial (Topeka) EarthCache

The Dwight D. Eisenhower Memorial at the Kansas State Capitol in Topeka honors the 34th President of the United StatesI. Located on the northwest corner of the Capitol grounds, the memorial features a life-sized bronze statue of Eisenhower in military uniform, capturing the moment he addressed his troops before the D-Day invasion. The statue was dedicated on October 22, 2018, and is a replica of the one representing Kansas in the National Statuary Hall Collection in Washington, D.C.

The statue rests on a substantial granite base, chosen for both its durability and stately appearance. Granite is a common choice for monuments due to its resistance to weathering and its association with strength and permanence. The granite base is what we will be studying for the topic of this earthcache.

Common Types of Erosion on Granite

1. Mechanical Weathering:

   • Frost Wedging: Water enters small cracks, freezes, and expands, causing the granite to break apart.
   • Abrasion: Physical scraping by wind, water, or other rocks.

2. Chemical Weathering:

   • Oxidation: Minerals within the granite, like feldspar, react with oxygen, leading to discoloration and weakening.
   • Hydrolysis: Reaction of minerals with water, transforming feldspar into clay and causing surface deterioration.
   • Acid Rain: Sulfuric and nitric acids in rainwater react with the granite’s minerals, accelerating decay.

3. Biological Weathering:

   • Plant Growth: Roots penetrate cracks, exerting pressure and expanding fissures.
   • Lichen and Moss: Organic acids from lichen and moss slowly degrade the rock surface.

4. Thermal Expansion:

   • Repeated heating and cooling cycles cause the granite to expand and contract, leading to cracks and surface flaking.

5. Water and Wind Erosion:

   • Flowing water smooths surfaces, while wind carries abrasive particles that polish or pit the rock.

Biological Weathering Impacts

The growth of Trentepohlia algae within the engraved letters of the Dwight D. Eisenhower memorial could contribute to the weathering of the granite over time. As the algae thrive in the moisture-retentive environment of the stone, they can produce organic acids and other compounds that may slowly break down the mineral structure of the granite. The presence of algae also promotes the accumulation of moisture, which can lead to physical expansion and contraction of the stone, potentially causing small cracks or surface erosion. Additionally, as the algae die and decompose, they can leave behind organic material that may further stain the surface, accelerating discoloration and wear. Over extended periods, the combined effects of biological activity and moisture retention could lead to noticeable degradation of the granite, particularly in the detailed engraved areas where the algae are most concentrated.

Environmental Exposure and Uneven Weatherin

The physical orientation of the Eisenhower memorial and the surrounding landscape plays a significant role in how different sides of the granite structure experience weathering over time. Due to the sun’s consistent path — rising in the east and setting in the west — the eastern and western faces of the memorial are subjected to regular daily cycles of heating and cooling. This thermal fluctuation can cause expansion and contraction in the granite, especially on surfaces that receive intense morning or afternoon sunlight. Over time, this can lead to microfractures and surface exfoliation, particularly in areas that undergo repeated stress from sunlight followed by cooler nighttime temperatures.

In addition to solar patterns, prevailing wind directions can amplify weathering on specific sides of the memorial. In Kansas, prevailing winds typically come from the south or southwest, which means the north and east faces of the monument may be somewhat shielded, while the south and west faces are more frequently exposed to direct wind-driven rain, dust, and airborne pollutants. These particles can have an abrasive effect, physically wearing away at the stone surface. Moreover, wind can carry moisture and pollutants that contribute to chemical weathering — for example, rain mixed with airborne carbon dioxide can form weak carbonic acid, which slowly dissolves minerals within the granite, especially feldspar, over time.

Chemical weathering may also be accelerated on the sides of the memorial that remain shaded for longer portions of the day. Less sunlight means these areas retain moisture longer after precipitation or morning dew, creating favorable conditions for chemical reactions and biological growth, such as algae or lichen. In contrast, sun-exposed sides may dry more quickly, reducing the duration of chemical interaction but increasing thermal stress.

Additional environmental factors such as nearby vegetation can also influence weathering patterns. If trees or shrubs grow close to one side of the memorial, they may trap moisture or drop organic debris that decomposes on the surface, contributing acids that chemically break down the stone. Runoff patterns during rainstorms may also concentrate water flow along certain sides, compounding erosion and chemical alteration of the granite.

Overall, the interplay of wind, sun exposure, moisture retention, and biological activity creates a dynamic environment in which each side of the granite memorial may weather at a different rate. These variations help explain why certain engravings or surfaces may appear more faded, stained, or eroded than others, even though they are part of the same structure and material.