Garden Hill

This Earthcache takes you to the summit of Garden Hill at the Kangaroo Ground War Memorial Park. Garden Hill and the surrounding 2000 acres are probably the remains of an extensive sheet of lava that once flowed down a shallow river valley. Possibly there were two flows. Early settlers considered the area an extinct volcano.

The Tertiary Period (Geochronology)

(Taken from Encycolpaedia Brittanica)

The Tertiary Period is an interval of geologic time lasting from approximately 66 million to 2.6 million years ago. It is the traditional name for the first of two periods in the Cenozoic Era (66 million years ago to the present); the second is the Quaternary Period (2.6 million years ago to the present). The Tertiary has five principal subdivisions, called epochs, which from oldest to youngest are the Paleocene (66 million to 55.8 million years ago), Eocene (55.8 million to 33.9 million years ago), Oligocene (33.9 million to 23 million years ago), Miocene (23 million to 5.3 million years ago), and Pliocene (5.3 million to 2.6 million years ago).

The Tertiary was an interval of enormous geologic, climatic, oceanographic, and biological change. It spanned the transition from a globally warm world containing relatively high sea levels and dominated by reptiles to a world of polar glaciation, sharply differentiated climate zones, and mammalian dominance.

The Tertiary Period saw huge alterations in Earth’s systems and the development of the ecological and climatic conditions that characterize the modern world.

Soil types

(Taken from Australian Plants Society of Victoria website apsvic.org.au)

Soils are usually classified as gravel, sand, sandy loam, loam, clay loam or clay. A simple method to determine soil type is to take a slightly moist sample in your hand and squeeze it: …

Gravel or sand - Soil fails to compact and runs through your fingers.
Loam - Soil compacts slightly but still fragments through your fingers.
Clay - Soil remains as a solid mass.

Soil structure

Structure is the way soil particles group together. Some soils, such as beach sand, have particles which do not cling together and therefore have no structure. Some clay soils cling together in one solid mass and therefore also lack structure.

Well-structured soils break up easily into fragments of irregular shape and size. These fragments do not completely fill the space they occupy, leaving a network of open spaces and passages in which plant roots can grow and allowing water and air to be taken in and excess water to drain away. Most plants need air and water near their roots to grow well.

GRAVELS - Have little ability to hold water or retain fertilizers, and are naturally very low in plant nutrient. They make an excellent mulch, however, it is difficult for plants to survive in them unless clay and loam are added to hold moisture and nutrients. Deep rooted plants from gravelly soils, once established, will survive in them, because moisture is often present at depth.

SANDS - Have similar characteristics to gravel but do retain some moisture, especially as depth increases. Often sandy soils become more compacted as depth increases and tend to have more of a sandstone profile. Their drainage is excellent and many plants from sandy areas, such as Western Australian Banksias, have adapted to survive in these nutrient-deficient soils.
The top 100mm plus of sandy soils can be water-repellent due to wind-blown particles. This can be overcome by digging in humus, clay or loam soil to give a much better water retention profile. Alternatively, the top 100mmm plus can be removed from the proposed planting area to expose the more porous sand below or soil wetting agents can be used.
Near the sea, calcareous soils may be found which, due to their poor structure, accept very little moisture and it can be very difficult to establish a garden unless using local native plants.

LOAMS - Often found where market gardens were once established. Much of south-eastern Melbourne consists of these soils. They have good drainage while retaining some moisture and allowing plant roots to readily penetrate downwards. Native plants are easily grown in these soils.

CLAYS - Heavy soils that can retain a lot of moisture, but when they dry out and crack they are hard to dig. They have plenty of plant nutrients.

Victoria has a wide variety of soil types that reflect differences in soil forming processes dictated by factors such as geology, landform, stream activity, vegetation, climate and age (i.e. degree of weathering). Soil underpins the productive potential of Victorian agriculture and forestry. The basalt soils of Kangaroo Ground are very isolated and specific relative to the cast expanses of basalt encompassing much of the western district. The earth here derives from ancient volcanic activity here many millions of years ago during the Miocene period (22 to 6 million years ago). Over these many years, the lava flows have since broken down to the deep rich loamy basalt that surrounds this area. Many of the soil's components result from the life cycle of plants and animals that have occurred over the many thousands and millions of years since the volcanic activity. The soil here is probably a consequence of the intensive farming as well as the original basalt base.

Looking from the viewing platform to the road escarpment opposite you can still see the ancient lava flows.

The basalt at Kangaroo Ground is part of 'Older Basalts' that underline the Red Loams (such as Gembrook and Emerald). These red loams are kind of fossil soils, going back to a distance climate much wetter and warmer in the Tertiary Period.

To successfully log this cache please use your own judgment and the information provided above to answer the following questions and send us your answers to the best of your ability;

1. Take a look at the soil in the grassy area surrounding the viewing platform. How would you describe the colour of this soil? You may need to use an object such as a key to inspect the soil if there aren't any exposed sections, but please don't leave any lasting damage to the area.

2. Based on the information provided and your observations, do you think this soil is an example of gravel, sand, loam or clay?

3. Based on the information provided and your observations, why do you think the soils here are so different from its surroundings?

4. Provide a photo of your team, team name or GPS near GZ. Include this photo in your log, but make sure it doesn't show any of the answers.

You are welcome to log straight away to keep your TB's and Stats in order but please message us with your answers within 10 days. Cachers who do not fulfil the Earth Cache requirement will have their logs deleted.

Congratulations Long John Silva for the FTF