Rano Kao Expedition 2008 (RKE08)
Rapa Nui
March 17-29

It had been almost exactly three years since my last visit to Rapa Nui, and Rano Kao specifically. But in 2005 it was very different on the lake than what we found this time. I will discuss the findings later in this summary. Meanwhile, I organized a new expedition that included myself, Ki Istre from Seattle, Washington, Rosanne Hawarden, from Christchurch, New Zealand and Michael Osborne from Stanford, California. We are otherwise known as the Rano Kao Expedition of 2008.

In 2005, I along with the help of John Flenley, David Meek, Rob Dunbar, Yan Araki and Francisco Rapu obtained 3 sediment cores from Rano Kao. These cores were taken at various points around the lake while another attempt rendered over 20 meters of water and obtained no core. The one near to center of lake, called KAO3, is the one that I have chosen to work on for this PhD. KAO3 consisted of 2 meters of floating Totora/Polygonum mat that were collected from the surface of the lake with a D-Section corer. Below this mat we found 10.5 meters of water and 9 meters of sediment below til we maxed out the Livingstone corer.


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Chart One. Radiocarbon dates of KAO3, Rano Kao, Rapa Nui March 2005.


These 9 meters were radiocarbon dated by using Scirpus seeds to give a very good linear chronology ranging from 1,000 years BP at top of sediment to 15,000 years BP at bottom of core. (see chart one above) It seemed the modern to 1,000BP was trapped in the floating mat. This same conclusion was also found by John Flenley in his KAO2 core taken in 1983. (see chart two below)

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Rano Kao Expedition 2008 Group Photo – (left to right) Michael Osborne,
Candace Gossen, Ki Istre and Rosanne Hawarden.

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Michael and Alejandro at core site 1

Objectives of This Research Travel (stated in proposal January 2008):

1. Core floating mat that ranges from 2-3 meters in thickness. Obtain a minimum of 5 cores.
Near to lake sediment core location from 2005 KAO3, as well as interesting parts of mat that may be dead, or have unique features.

2. Lake bottom survey. Using original core location, set up at least one transect line across lake in as many depth points as possible.
To confirm mysterious trenching found in core.

3. Plant specimens. Collect inflorescence of totora, and polygonum. Rhizomes and plant matter of both. Also other plants growing on mat including moss, fungi, and small plants. Photograph, collect seed, and some plant matter. Conduct walking survey around crater to locate plants types, collect seed and photograph.

4. Photograph coring adventure, plant collection, survey, and all pertaining to research to compile a documentary both for dissertation and education.

5. Sample Palm Root cast. Take soil sample in root cast to identify pollen, and whatever else may be located within the casts.

6. Petroglyph photograph and identify known areas that have plant relation. (Conversation and advice from Georgia Lee)

7. Mineral collection in crater to help identify minerals in lake sediment core.

Remaining work and analysis once cores return to USA

o Ship cores to LRC = $75? depends on weight
o Archive and identify and scan the cores at LRC – Candace Labor and time while in Minn.
o Sample and pick seeds for RC dating 4 locations = $2400 or use dating of existing dated mat?
o Sample for isotope analysis (10 samples at 20cm intervals = $1200 or 20 samples at 10cm intervals = $2400)
o Sample similar for pollen samples and process at UMN – Candace labor and time
o Sample similar for raw sediment macrofossils at UMN – Candace labor and time

Course of Events:

Upon landing on Rapa Nui I was faced with many challenges, which is expected, but it set the course of time for getting done all that was needed.

First one on the island was Rosanne, who greeted me at the airport. We looked around for our person we were to meet that Sonia had set us up with for stay at the Farmhouse. Noone showed so we proceeded to my friend Niko Haoa and the Hotel Otai for advice. We ended up in a much more suitable location to stay, with Selma Tuki and her little house next to the Otai. The stay with Selmas was wonderful and we all quickly became great friends.

The next day 3 days I spent visiting CONAF to obtain a permit to work on the island. I had been writing to Enrique Pakarati as I had been advised but quickly realized he was the wrong person to talk with about working on the island. CONAF representative Ricardo Crisostomo and Enrique Tuki and I met finally on Friday and typed up a permit and exactly what I was going to do on the island. 4 stamped copies and I was on my way to begin the coring once the guys arrived tomorrow.

Saturday Mike and Ki were on the same flight from Santiago, and quickly I saw Ki come off the plane with a great big smile. Rosanne, Ki and I waited outside the airport as every last one of the tourists departed and we stopped and looked at each other “where’s Mike?” There he came, delayed but he had arrived.Tired and weary, we walked a bit, got settled, ate, and planned our course for the next day.

Sunday, was Easter on the Island. How appropriate we should be there on the European namesake, but it came and went without much affair. Those that did care celebrated, those that used the occasion of holiday spent the time with their families camping and on the beach as it was 29C.

Sunday was also our first work day. We decided to survey the lake and take the water samples and be prepared for our Monday first day of coring. Everyone was quite surprised at the enormity of the lake and ominously looking down saying

“we are going down there?”    wpe12.jpg (7494 bytes)   


as we proceeded to walk down 250 meters to the lake surface,

thru the Acacia and Avocado trees on a steep incline of some 60 degrees.         wpe2.jpg (8046 bytes)

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We proceeded to walk out of the forest that had been planted in the 1970s to help soil erosion, and looked up totora as tall as the trees, over 4 meters tall. This was the first adventure for the others to “walk on water” or at least trek thru the water, on matted roots of polygonum and totora.

For about 20 meters we walked thru the stands of totora, falling in a few holes along the way, saving the camera! We arrived onto a hardened mat surface of ferns that gave us strength to walk on the mat. We came about within another 10 meters 3 trees that had firmly rooted themselves about 30 meters from the lake edge onto the inwashed sediments and water. It was quite a site. We proceed to try to find a path thru the totora, on the ferns towards the center of the lake.
Quickly we realized a pattern, dark mat with moss was soft and one plunged thru to mid-calf, stay on the ferns they kept it firm, and they were very abundant. It was truly a wet winter to have so many, much more than I had noticed from the very dry mat 3 years before in 2005.

We walked and took waypoints and depth readings whenever we could, and it became an arduous task to get around the water holes and be able to see thru the totora. As it was quite surprising to be walking thru the totora and fall in knee deep. So we obtained 5 waypoints noted on the GPS, and took depth readings with a sonar depth reader (fish finder) that also told air and water temperature. We stopped at waypoint 5 near a 12 meter hole in the mat for the water samples. (see waypoints and coring points on google earth map below)

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This time I brought a water sampler that allowed me to take water samples at varying vertical depths of the lake and the chemical analysis was conducted partially on lake and completed at the house back at camp. Results below:

Waypoint Information (reference photo above for locations):

Stop1    27.18218 S lat., 109.43793 W long. NE edge of Lake

Totora very tall over 3 meters. Thick and triangulated, culms on top but not sure of maturity of seed within. Novembers culms were too young and had immature seeds. We will find out at camp what these contain. Walking thru Acacia, fern and avocado trees. Lots of ants on the trees, that climb onto you instantly but don’t seem to bite. If you touched a limb they would be all over you. But the thorns on the trees coming were down were like daggers of up to 1” long, so you must keep your balance or be bludgeoned.
Mosquitofish were abundant in the lake, many on the edges that were minnow (bait) size of 5cm long. The slopes in the forest had many ferns and long grasses that drapped over the side like hair. A few snal shells were found along with obsidian pieces on the paths.

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Stop 2    27.18253 S lat., 109.43795 W long. approximately 30 meters from the NE edge of lake

From edge of lake approximately 30 meters to the south of entry point from path. Tall totora on the lake edge measuring 4 meters tall and thick triangulation of 5-6cm. Deep water of a meter to the top of the root surface, tripping and falling until up on the mat surface about 20 meters out. Distinctly different from the edge of the lake which had polygonum and other plants to be identified growing in the shallow waters. This is approximately where the 3 trees were growing.

Stop 3    27.18343 S lat., 109.43866 W long.    First open water probe

    Water Temp: 25C
    Depth: 5.2 m (sonar)
    Rope: 7m (weight rope)
    Black clear water
    No smell

Polygonum taking over a dead patch on the mat surfacewpeA.jpg (10390 bytes)

Stop 4    27.18432 S lat., 109. 43815 W long.

    Water Temp: 25C
    Depth: 1.5m
    Rope: 1.5m
    Black clear water
    Smell of sulfur? or some strong odor

It seems some of the water pools that we see from above are really shallow water collecting on top of the mat from the very wet winter. Therefor the 1.5 meters of water we are measuring is the rainfall for the winter that has collected on top of the mat.
Collected sample here of dead matter from mat surface.    wpeB.jpg (8151 bytes)
                                                                                        variety in the mat, dead dry patches, patches with new growth, dark                                                                                          brown wet patches with moss on surface, and totora patches between.

Stop 4b    27.18437 S lat., 109.43812 W lat.     

Water Temp: 25.5C
Water Depth: 7.9m
Rope: 8.2m
Black clear water
No smell

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Stop 5    27.18465 S lat., 109.43820 W lat.

    Water Temp: 25C
    Water Depth: 12.2m
    Rope: 12.4m try one, 12.4 try two, 13.2 try three (rope tends to slide down slope which may add additional length as we discovered the mats have shallow shelves at they slowly decompose into the water.

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Water Quality Testing: Location:    Stop 5    27.18465 S lat., 109.43820

location Depth Water Temp pH nitrate phosphate DO Turbidity BOD (5days)
Surface surface 26C 6.0(good) <5ppm (excellent) 0.5ppm (excellent) 3ppm(poor 26C/4ppm=49%) 0JTU 3ppm(excellent)dO=0C
Mid 6m 24.5C 6.0(good) <5ppm(good) 0.5ppm (excellent) 4ppm (24.5C/4ppm = 48% poor) 0JTU 2ppm (excellent)dO=2C
Bottom 12.2m 23.5C 6.0(good) <5ppm(good) 0.5ppm (excellent) 4ppm (23.5C/4ppm = 47% poor) 0JTU 1ppm (excellent)dO=2.5C

    no fecal coliform test conducted, as did not want to contaminate water or island with foreign bacteria to test                            

Water Temps collected on site in water sampler and then placed into 3 different colored Nalgene Lexan bottles for further testing that was conducted within 2hours of retrieval.

Testing procedures:
1. pH was tested with dissolved tabs
2. phosphates with dissolved tabs
3. dissolved oxygen with dissolved tabs
4. BOD water in tube, wrapped in alum foil for 5 days then tested the same as for dissolved oxygen with dissolved tabs
5. nitrates with dissolved tabs
6. temperature in field with fish finder in collection tube (1.5litre)
7. when all tests were completed, remaining water was poured into white container with turbidity secchi disk.

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Weather and Climate Information:

When we got to the island we discovered that there had been a drought for the past 5 months. Noone was having problems with water as yet, as the people of Rapa Nui get their drinking water from the aquifer under the island which I have been told contains millions of liters of rainwater.

The drought though had a bad consequence on the trees and plants though, as there was a plaque of insects that were devouring all of the leaf matter in search for fluids. These little buggers were no local and not wanted, but the plight of importation of food. Invisible little eggs that come along on the skin of oranges and in the wood of crates, and amongst the hundreds of tourists that land on the island every day. CONAF was working really hard with sticky cards dated in all of the places they had observed these insects. I walked quite a bit in the Rano Kao area as well as Hanga Roa, the little town and noted the trees and plants that had these cards. All of the cards had been hung within 7 days of my landing on the island, so there was a diligent watch on these bugs.

Although quite interesting where all the water is in the lake, I saw no insects such as I had seen on the trees in the town. I was glad for that.

Previous to this drought, there was a very wet winter. Wetter than most I was told. And I verfied that observation by noting small pools of water 1.5 meters thick on the floating mat of the lake. I had not seen so much water present from above as I first thought looking down, and then once on the mat I realized that these were not open water holes between the mats, but collected water on the top.

This wet winter, heavy rains made everything green at Rano Kao. The totora flourished and covered the entire lake. What had been an open middle in 2005 was now covered with thick ferns and totora growing to the middle of the lake. I came across new rhizomes of totora that were just branching outward with their typical two-finger size rhizome thickness and running 7-10 stems per rhizome ranging from tall to new emergents. The rhizomes were about 20 cm below the surface in a wet, brown mossy like mixture, a perfect peat.

The totora was also taller than I have ever seen on the edges of the, while the polygonum grew vertical at the edges, it was also spreading horizontal into the open pools with its suspended reaching into the open water. I could see how the mat was forming, it was taking advantage of the dying patches by invading and using the nutrients while expanding its thick roots outward and interlocking to branch across the lake. I put myself back in time and imagined the same thing happening when the mat was forming for the first time, or maybe many times in the ancient past.

Linking Weather Patterns:

This weather event of a really wet winter and then drought on Rapa Nui, also followed patterns that I had seen in Minnesota and Portland this past year. While in Minneapolis fall of 2007, rain came in September which was unusual for this area, and snow started at Thanksgiving and hasn’t let up yet and it is April 2008. The talk around here is that there are record snowfalls, and it is late in the spring for snow to be falling, but it came yesterday, only 3 days after feeling 76 degrees and sun here. They say this is Minnesota weather and I hear the farmers talking about a trend, that happened 10 years ago all the same, a really wet year. And planting that could not happen before Memorial Day as it would be freezing again soon.

Meanwhile in Portland it has not stopped raining, and it has hailed with snow a few times in the city. Mt. Hood is not closing for the spring whereas it is common for the past years to be closed in Mid-March. There is a 222” base and growing still of snow. Its wet, there is moss growing everywhere and all are waiting for spring, including the trees that have all bloomed.

But is there a connection between the wet winter that fell on Rapa Nui, that then followed by Portland and then Minneapolis? Yes it is the same, and also if one looks back when I arrived in Portland in 1996, it was the year of great rainfall and an almost overflowing Willamette River. 12 year cycle? La Nina? Could the El Nino and La Nina cycles also affect the planet the same whether it be 27deg South or 45 deg North of the equator? Can we find clues on Rapa Nui that are linked to already known observations in North America? These are good questions. But for me I experienced them all, I am the observation tool and overtime and the older one becomes the patterns emerge that we see and remember about change.

Coring the Lake:

Sunday, the day we surveyed the lake and took water sample was the last day of the drought, because come Monday it rained very hard and messed up the plans for the first day of coring.
THAT is why one must allow extra time on an adventure, rain, and getting permits!

Tuesday March 25, Rosanne, Ki, Mike, Alejandro and me hiked down into the crater into what looked like ominous clouds folding over the crater rim. By the time we reached the bottom we could see it coming in over the rim and sinking down to the lake very fast, then the rain, lluvia and Ua in all three languages, English, Spanish and Rapa Nui came and fell. It came with torrents of rain. We hung out in the trees for an hour and waited and hoped we could get out on the lake, but to no avail it was not leaving.

So we left the gear in the trees hidden well, and hiked out soaking wet.

The day was not wasted though, as we later went to Rano Raraku and collected totora samples at the lake so that Heather at UC Davis could conduct DNA identification on both stem and seeds samples from Rano Raraku and Rano Kao. We also had fun walking around the place as my three friends had never seen the Moai Quarry.

Core 1    27.18442 S lat., 109.43832 W. long
Water Depth: 12m

Finally Wednesday was a sunny day. Rosanne off to New Zealand didn’t join us. Ki was the plant collector, so Mike, Alejandro and me started off in the direction of the water sample stop 5 but focusing more inward to the center of the lake if we could. The totora is tall, the water is high and we stopped a core spot 1 that was firm on a bed of ferns in a totora patch.

We began taking 50cm sections, and ended with a total length of 4 meters. This was unexpected as the KAO3 mat core only had 2 meters and John Flenley’s mat cores were also 2 meters. So were we in a place where there was deeper mat, would be able to recover the missing 400 years between the bottom of the KAO3 mat and the lake sediment cores? or was this a spot with in-washed sediments that made the appearance of a thicker mat? We maxed the coring rods that I brought so we had to stop. Not sure if we could have collected core deeper but it seemed the bottom 4th meter was watery which is a sign of the barrel not closing correctly due to a lack of resistence, no core.

The core was fibrous, good and linear 2 meters long. Not many gaps. Core identification has already begun on this core and I have archived the cores, scanned for magnetic susceptibility, and described the sections. I have noted in the smear slides for this core that there is charcoal in all of the sections, as well as what appears to be tehpra, and glass particles in the bottom section at meter 4. There is definitely human presence in this core.

This core was easy to get, cutting thru the mat was not difficult as it was very wet. In comparison to 3 years ago it was dry and very hard. The biggest challenge was getting a contiguous core with no gaps or missing parts. This core seems the best of the 4 collected on this expedition.

We collected a 2.5 meter core, but then could not get the rods apart. We radioed Ki to ask CONAF at Orongo for some help with the Park rangers, but noone had wrenches nearby. So we were stuck on the mat, some 200 meters out with a 4.5 meter long corer that was stuck together. We couldn’t walk up with it, nor core again as we couldn’t turn the small diameter tubes enough to collect more core.

So this very nice sunny day, was cut short and we had to return another day to finish more cores
It has now begun to rain everyday so it is very unpredictable on this Wednesday, what Thursday or Friday may be like. But we have to come, we cannot leave with having one core.

So we stashed the corer in the totora thanks to Alejandro, hid the bag in the trees and hiked out. Ki made two trips up and down, but little did we know he had 101 fever and was soon to get real sick.

Cores 2 and 3    27.18365 S lat., 109.43653 W long.
Elevation: 110m,
Water Depth: 12.2 m (12.7 with rope),
Water Temp: 23.0C
Today weather is holding. Clouds are forming and moving over the island. It rained hard overnight and everything was wet upon waking. We decided to go rain or shine.

It was good on the lake, cool while we found out later it was raining really hard at Hanga Roa. Strange this island has pockets where it rains and stays dry in other locations. The island is only 14 miles at its longest and it seems so small to have varying weather patterns but it does. But today we had Kon Tiki, the Sun God with us. Alejandro, Mike and me. Ki sick in bed with cipro and a 101 fever.

We tried to take a trek heading off towards the east rather than the path we had taken before. This time we tried to find the water path we had seen above. We ended up stopping near a large water hold with 12.7 meters of water.

Tried several places but couldn’t get good consistent cores. Polygonum was growing on the edges of the hold with ferns. Inside it was dark brown moss. We took core 2 and moved a little farther away for core 3. No problem with the corer and the wrenches we brought with us, 3 of them!

Core 4    27.18403 S lat., 109.43675 W lat.
Elevation: 108.5m
Depth: 12.2m
Water Temp: 23.0C

This core was the last. We reached the end of the tubes that we had brought.
We again searched out a placed near to another water hole towards the center of the lake.

The core was 3.5 m deep. Mike thought at 2 meters he was at the water because of little resistance but came up with a full core and continued down to 3.5 meters. The next 50 cm after that was mostly water as the cover didn’t close. Usually a sign there is no resistance and below mat.

We secured the cores then I told Mike I was going in for a swim. He got to it first and took a dive in. The water had a distinct thermocline in this hole. it was very warm at top, but only a meter below it was very cold. We swam across and took a depth reading with the waterproof sonar at 11.5 meters. Then came back and tried to get a vertical profile of the mat, and realized that the mats sink on the edges and provide a shallow ledge as it folds into the lake.

I also realized that since it was so difficult to get to the center of this lake and take a proper profile of the bottom, I would have to swim thru the holes to get it done next time!

Serendipity also was with us on the walk about. As Mike was walking around to find a new path he yelled at me to say there was obsidian in the mat where he was. I was trapped on another floating island and said he remind me when we leave to head that way, but by the time we wrapped up, soaking wet in that black clear water, I forgot. So somewhere on the lake is an ancient pile of obsidian, large enough he said that definitely looked flaked. and it was in as dead brown patch, not the grey dried up stuff, but the brown decomposing stuff.

Alejandro called this lake, Lago de Antigua, Aqua Dulce. It truly is the sweet water of the ancients.

Objectives Achieved:

1. Core floating mat that ranges from 2-3 meters in thickness. Obtain a minimum of 5 cores

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Photo above: Profile view of coring spots in relation to the mirador at the rim. Directly ahead on the edge of the rim and to the left of the marker is the site of Orongo. Photo below: lake surface view of coring points.

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LRC Archive Data Sheet

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2. Lake bottom survey. Using original core location, Set up at least one transect line across lake in as many depth points as possible. To confirm mysterious trenching found in core.

As stated above, “I also realized that since it was so difficult to get to the center of this lake and take a proper profile of the bottom, I would have to swim thru the holes to get it done next time!”

This objective was not completed. With the new growth of Totora over the lake, and the amounts of water pools and holes, it was very difficulty to maneuver. It would take swimming from hole to hole to actually run a transect line across. If one could meander aimlessly on all available mats then there might be a number of points taken to make some sense.

But for now the mystery of the missing sediment still lies in the depths of the lake. And I shall still contemplate how to get this done on the next expedition!

3. Plant specimens. Collect inflorescence of totora, and polygonum. Rhizomes and plant matter of both. Also other plants growing on mat including moss, fungi, and small plants. Photograph, collect seed, and some plant matter. Conduct walking survey around crater to locate plants types, collect seed and photograph.

Most of this objective was completed. Samples were taken for totora at Rano Kao and Rano Raraku and sent on to Heather at the UC Davis who will be conducting DNA and nutrient identification on the seeds and stems of the totora. Since she collected totora at 45 sites between North and South America, we hope to be able to identify these current plants into some association with others locations, answer the question of introduced or native plant, and if there are different species of totora existing on the island. The seeds that I have identified and used in the radiocarbon dates vary and I will also use the collected modern seeds as a comparison to the changes in seed overtime to once again, identify change over time in the lake environment, species type and perhaps some link with human use of the plant.

A totora rhizome was collected and is now in portland in a pot hoping to live and be studied. Samples of plants that were living on the mat were collected and pressed into a specimen identification book for further identification as to the native plants on the lake. Photographs were also taken in order to preserve the living environment and understanding of the variances of this lake ecology.

A walking survey was not conducted as we ran out of time due to rain. Although species of plant were identified from afar: Sugarcane is a very bright green and with cameras we could see patches on the east and west slopes of the crater that are growing wild, although once cultivated on the slopes. There are also grape plants, with an unknown species yet to be determined growing on the north slope of the crater. Banana plants were also seen on the slopes again wild. Growing near to the hiking paths are avocado and Tuyaba or Guayaba.

wpe18.jpg (6289 bytes) Ki, me and Alejandro (a very wet day on the lake)

wpe19.jpg (14343 bytes) After the swim


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From the Moai Quarry looking at Tongariki, me, Mike and Rosanne (ki behind the camera)

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that’s all folks……..


Many thanks to all that helped along this way to get there, to be there and to come home!

Enrique Tuki and Ricardo Crisostomo CONAF; Eric Alarcon and Eugenio, SAG; Selma Tuki; Nico Haoa; Chris Stevenson and Aviva/Earthwatch;  Aquatic Research Instruments; Anders Noran and Amy Myrbo, LRC; Rob Dunbar and Mike Osborne; Rosanne Hawarden; Ki Istre; Alejandro Naoa; John Snodgrass; and my Aku watching over us at the island.

and a special thanks to John Flenley and David Feek, for being my mentors in teaching me how to core at Rano Kao a few years ago, who I will be forever grateful to.