It’s been over a month since I posted a “Monday Geology Picture”. Apologies for that — I was traveling (4 weeks in a row!) and was very busy. Anyway, I’ll try to post regularly again now. Today I’m sharing an impressive example of biological weathering, which is when a living organism contributes to the weathering of a rock. In this case, large tree roots are breaking apart a sedimentary rock. I took this picture yesterday when I was hiking on Table Mountain here in Cape Town with my family.
Yesterday morning I flew back to Cape Town after a business trip. I arrived a little after 7 am and was treated to a stunning view of Table Mountain and Lion’s Head as I flew in. I’m sharing a picture I snapped of that view as this week’s geology picture. Here’s a closer look as well:
I am lucky to live in such a beautiful city! However, you can see that the city is looking somewhat brown and dry, due to the drought and water restrictions. No one is watering their gardens!
For this week’s post, here’s a picture that I took yesterday during a Sunday afternoon hike with my family. We went for an easy stroll, baby and all, along the Alphen Trail in the Constantia region of Cape Town here in South Africa. My son is 3 months old now, and we’re just starting to go on some easy hikes as a family. The Alphen Trail is more of a walk than a hike, but nevertheless it was nice to spend some proper time outdoors again! In another month or two we hope to embark on some proper hiking.
There is too much vegetation along the Alphen Trail to see much geology, but along one part of the trail I did notice some interesting large granite boulders, which are shown in the above picture. These boulders no doubt belong to the ~550 million year old Cape Granite Suite. Large outcrops or boulders of these granites are commonly seen in the Cape Town area. For example, you can see large granite boulders at some of Cape Town’s beaches. However, I found these Constantia granite boulders interesting due to their weathering. While still quite large, there are clear signs that these boulders are being broken down through weathering. On the right, you can see a nice example of exfoliating granite weathering. On the left, you can see that a large boulder has split in two. In a few parts of the picture, you can see tree roots and other vegetation, which are no doubt contributing to biological weathering of the boulders.
Here’s a close-up view of the exfoliating slab:
Happy New Year! I’m going to do my best to blog more regularly in 2018, starting with this first “Monday Geology Picture” post. This week I’m sharing a view of Lion’s Head (the distinctive mountain in the background of the picture), an inselberg here in Cape Town, South Africa, the city where I live. I took this picture a few weeks ago during a walk with my family along Sea Point Promenade. Cape Town is a fantastic city — you can see amazing geology even when you’re downtown!
For this week’s picture, here’s a lovely view of an inselberg and the Twelve Apostles section of Table Mountain here in Cape Town, South Africa. Note the layers of sedimentary rocks of which the mountain is made. In the foreground, you can see some rocks of the Cape Granite Suite, which is about 550 million years old.
For this week’s “Monday Geology Picture” here’s a view of the Cape Fold Belt with a vineyard in the foreground. I took this picture yesterday when I took a short walk with some friends through a vineyard located in the Stellenbosch winelands, just outside of my home city of Cape Town. You can see some impressive folding in those distant mountains!
For this week’s picture, here’s a view of a salt pan on Intaka Island, a small nature reserve in the Century City area of Cape Town. I often go to Intaka Island to paddle in a kayak on the canals surrounding the island. On Saturday morning I went for one of my usual paddles, and then in the afternoon I joined some friends for a nature walk on the island itself. During the walk, I snapped this picture of the salt pan on the island. The island nature reserve was founded to protect plants, bird, and other wildlife in the Century City area, which has been substantially developed since the late-1990s. In the background of this picture, you can see cranes where a block of apartments is being built on one of the last areas of open ground near the reserve. Table Mountain is also visible in profile in the background. Amidst all the development in busy, growing Cape Town, I’m glad that a few parcels of land, such as Intaka Island, have been set aside for conservation. I enjoy visiting Intaka a couple of times a week as an escape from the hustle and bustle, and all the concrete, of city life. I’ll have to share some more pictures of Intaka Island in a future post.
Earlier this year I visited a local wine farm here in the Western Cape of South Africa, and there I saw a lovely display of some reproductions of some old maps of Africa. I’m not sure about the background of these maps, but I snapped a few pictures because I thought they were interesting. If you recognize any of the maps, please let me know in the comments.
Here are a couple of close-ups of the detailed map of the Cape Town area, where I live:
If you look closely on the close-up view (click for a larger version), you can see that there are some useful descriptions on parts of the map. For example, there’s a description “Very Good Grounds” and then there’s a description “Grounds Not Fit for Tillage”. There are also some comments about the local mountain chains, with one being described as “Inaccessible Mountains” (I’ve corrected to modern spelling).
My husband and I live roughly in the “Grounds Not Fit for Tillage” part of the map, which probably explains why we struggle with our garden! The soil where we live is indeed very sandy and mostly comprised of quartz. Thus, it’s tough to grow anything other than local, native plants. So, we’ve planted a garden full of local succulents and are attempting this year to grow a few vegetables in a raised bed. We tried planting some flowers earlier this year, but only the ones in the pots (with special soil) seemed to survive!
I think that “Inaccessible Mountains” description may be fair, too. I’ve been on some tough hikes in that area!
I really enjoy old maps, and it’s great when they contain detailed information such as the Cape Town area map. I’d say that this map is still useful today!
For this week’s “Monday Geology Picture” here’s a shot of a pretty granite boulder that I spotted during a forest hike in the Constantia region of the Cape Town, South Africa. No doubt, this boulder consists of ~550 million year old Cape Granite. There’s no scale in this picture, but the boulder is about 2 meters wide.
Over the weekend I participated in a kayak race that was held in the lovely little coastal town Hermanus, South Africa. The race was held on a lagoon with a beautiful background of mountains that are part of the Cape Fold Belt. You’ve seen pictures of this fold belt before here on Georneys. For example, here the belt is featured in one of Callan’s “Friday Fold” posts. However, these mountains are so pretty it’s worth sharing another picture here. Enjoy!
Georneys 