Columnar Basalt at Black Point, D'Entrecastreau National Park

Black Point, D’Entrecastreaux National Park

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Absolutely everything you need to know about Black Point and the Bunbury Basalts

Standing on the the black rock pillars looking out to sea you could be excused for thinking you are on the Giants Causeway in Ireland, or even the volcanic wonderland of Iceland; but this striking headland is Black Point in southwest Western Australia. 

Black point is one of only a few basalt outcrops in Australia to show this dramatic symmetry and yet it is not well known about. Being not far from Margaret River and the camping and outdoor adventure hub of Pemberton and Nannup, you’d think this cool place would be a major attraction and yet we always have the place to ourselves when we visit.

It may be a bit of a bumpy four-wheel drive out there but believe me, it’s worth it!

Sunset at Black Point looking out over the columnar basalt

Where is Black Point?

Black Point is a rocky headland that juts out into the Southern Ocean about half way between Augusta and Windy Harbour. While only 270km from Perth as the crow files, it is a fairly rough 4WD drive out through the national park so it is definitely best to stay close by and start your journey into the park first thing in the morning. The following distances are only to the turnoff to Black Point on Stewart Road; from here there are three different routes in.

Distances

  • From Perth: 307km,  3hrs 15mins
  • From Pemberton: 50km,  40mins
  • From Nannup: 42km,  30mins
  • From Margaret River town: 85km,  55mins
  • From Mandurah: 241km,  2hrs 30mins
  • From Bussleton: 95km,  1hr

How do we get to black point?

From Stewart Road there are three routes to Black Point. Warning, they all require low range and high clearance. If you try and attempt to reach Black Point in a 2WD car I can guarantee you will get stuck in the soft sand.

  1. Black Point Road – 23km – head straight down Black Point Road all the way to the end and follow the signs. 
  2. Via Lake Jasper – 45km – After just 200m on Black Point Road take a left onto Pneumonia Road and follow all the way to the end. Here you turn right and pass the D’Entrecastreaux National Park entrance information board. Lower your tyre pressure here. Follow the track to Lake Jasper then along the Wapet Track following the signs for Black Point. This drive took us 2 and a half hours each way.
  3. Via Milyeannup – 40km – Head down Black Point Road and turn right on to Fouracres Road. At the end turn left onto Millyeannup Beach Road then left again onto Woodarburrup Road. Follow the signs to Black Point.

NOTE THAT BLACK POINT ROAD IS CLOSED IN WINTER

Always check the road conditions with DPAW before setting off. You can call the DBCA Donnely District office on (08) 9776 1207 to ask about road conditions.

What is there to see on the way to Black Point?

  • Lake Jasper picnic area and campground.
  • Twin Karri Beach
  • Jasper Beach
Enjoying lunch at Lake Jasper, D’Entrecastreaux National Park
Twin Karri Beach, D’Entrecastreaux National Park

Camping near Black Point.

There are so many camping options within D’Entrecastreaux National Park and the other wilderness areas close by, you definitely won’t struggle to find a lovely campsite.

Within Black Point itself there are two campsites;

  1. Humpback Hollow – 20 sites
  2. Seal Cove – 10 sites
  3. Alternatively you can camp at Lake Jasper

$11 per night per adult, $7 with concession card, and $3 per night for children (5yrs to 16yrs) You cannot prebook or reserve sites at this location. There are basic toilet facilities but no power or showers. Remember to Leave No Trace!

So, now you know where Black Point is and how to get there lets get on to the really interesting stuff!!

So what is this striking landscape make from?

From your first glimpse across the coastal scenery two things are bound to occur; firstly you will blown away by the beauty, and secondly you will find yourself wondering ‘what is this strange rock formation?’

The definitive mosaic of hexagons and polygons that form the black rock pavement, and the black pillars, are the telltale signature of cooling igneous rock. The distinctive black colour, so different from the pink and grey granites of Esperance and the Margaret River Region, is due to the iron- and magnesium-rich composition of the minerals that make up the rock. Geologists call this particular rock Columnar Basalt; or more precisely for this exact outcrop: The Bunbury Basalt.

Black Point looking out over the columnar basalt

Wait, what? Why Bunbury Basalt when that’s 100km away?

Well, this basalt is part of a much larger complex of igneous rock that stretches all the way  from Bunbury down to Black Point. It was all formed at the same time in the same event and it is given a name to group them together. This is called a ‘formation’. 

Why do we have basalt in southwest WA?

This landscape at Black Point may be impressive, but the story behind its formation is even greater! Just over 130 million years ago, while dinosaurs were still roaming the earth, Western Australia was still attached to Antarctica to the South and India to the west forming part of the supercontinent called Gondwana

At some point this supercontinent began to break apart (more about this later on) and while the continental crust was stretching and thinning, it formed cracks. Through these cracks hot magmas was intruded and erupts out onto the surface. As the stretching continues, more and more magmas erupts and starts to form new crust.. Eventually, the two pieces of continent have pulled so far apart they are no longer joined and this new oceanic crust is now being created in between. 

The Bunbury Basalt we see at Black Point, Bunbury and Capel is the basalt formed when India and Antarctica tore away (or ‘rifted’) from Western Australia.

“The volcanic eruptions in this area were enormous, with their total volume equivalent to forty million Olympic-size swimming pools, or nearly sixty thousand Melbourne Cricket Grounds,”

Dr Olierook, Curtin University – full article here
Beach at Black Point

Why is columnar basalt hexagonal?

As you know from baking a cake when materials heat up, they expand. The opposite happens when they  cool; they contract. The basalt magma would have been intruded at over 1000C (1830F) and as it cooled and hardened, it contracted taking up less space. This resulted in fractures and the most efficient shape (and nature always takes the path of least resistance) is a hexagon. When the cooling (aka heat transfer) was not uniform across throughout the magma body it can form other shapes hence you will find 5- or 7-sided shapes among others. 

Where else can I find the Bunbury Basalt?

You needn’t track out to Black Point to see these cool igneous structures, though I recommend you do 😉 you can see the exact same formation on Back Beach in Bunbury! The basalt has also been mined around Capel.

Black columnar basal at Back Beach, Bunbury

How old are the rocks at Black Point?

A team from Curtin University dated samples from Black Point in 2016 and calculated them to be between 132 and 136 million years old. (click here for full paper)

What does the Bunbury Basalt represent?

This is the really cool part of the story! Remember how I talked about how this basalt was formed when Antarctica and India started to rift from Western Australia? Well, there has been some debate about the cause of this in academic circles.

Did a large mantle plume – a big upwelling of super hot magma in the earths mantle – cause the continental break up? Or did the break up cause the upwelling? The chicken and the egg paradox!

The Bunbury Basalt is just one small component of a larger igneous province that stretches from Western Australia to India and south and westwards into the Indian Ocean called the Kerguelen Igneous Province. This Large Igneous Province (LIP) covers an area of about 1,250,000km2 and started erupting about 130 million years ago. Most parts of the Kerguelen Province are well tied to the Kerguelen hotspot (area of hot upwelling in the mantle) but recent dating of the Bunbury Basalts has shown them to date 10 to 20 million years earlier than the hotspot! It is now thought that the melt that later formed the basalts was formed itself by ‘decompression melting of a parent material with enriched geochemisty’. Now, I know that’s a bit of a mouthful! Simply put, way earlier in history (about another 400 million years) the rocks were affected during the formation of Gondwana in the first place and this change and contamination by other crustal rocks meant their melting temperature was forever lowered. When Gondwana started to breakup and the crust stretch, it lowers the pressure exerted on the mantle below and some of that contaminated material can now melt.

low temp + low pressure = melting

Dating of the Bunbury Basalt showed it erupted in three phases around 136, 132 and 130 million years ago.

You can read the full scientific paper published by Curtin University in Earth and Planetary Science Letters and a short article about the paper in the Curtin University News.

Black Point looking out over the columnar basalt

But wait, there is more!

As if that isn’t enough to strike you with awe, there is a little something else I need to tell you about. If you walk down from Stepping Stones back towards the mainland into the little cove there you will see another strange rock formation. Look carefully and you will be able to pick our balls and lobes about a foot or two across protruding from the cliff face. This is actually lava! If you image the kind of lava you see in Hawaii, the bolus red sticky lava (see photo below of me on honeymoon looking all goofy and happy), this is called Pahoehoe Lava. When this cools it forms the lobes you see on the beach at black point.

Pahoehoe : basaltic lava forming smooth lobes or ‘ropey’ structures

Jed and Suzy standing on the emergency access road beside the active lava flow – Kilauea Volcano, Hawaii

So the pillar formations were formed from a big deep pool of magma that cooled relatively slowly – probably when a large flow filled a river valley for example; the pahoehoe would have been flowing over the surface with each lobe cooling to form a crust (even if the centre was still red hot) before the next lobe flowed over the top.

Pahoehoe lava lobes exposed in the outcrop at Black Point

So there you have a full description of one of the most geologically fascinating places in Western Australia!! If you want to know about more cool geo spots check out these blogs below 🙂

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2 comments

Call Suzy :)