<p>In a topological sense, if it's connected by an isthmus then it isn't an island. That doesn't mean that it might not be called that - but the answer is a cultural &amp; political one, and hence won't adhere to strict definitions.</p>

CC BY-SA 3.0
2015-09-26T06:21:55.003Z
2015-09-26T06:21:55.003Z
Semidiurnal Simon
<p>I think the naming difference is largely qualitative and even arbitrary in some cases. There are lots of 'islands' that are technically connected to a larger landmass by an isthmus of some sort, which would make them peninsulas technically, and not islands.</p>

<p>If you take the definition of a peninsula to be a body of land surrounded by water on three sides, then yes, the island in question could technically be called a peninsula. </p>

<p>Local names of landforms are often linked to cultural or historic influences, just as much as they are to their technical description. There's no 'threshold' of isthmus-width (as far as I'm aware), where once crossed, a peninsula-like island becomes an island-like peninsula . If there was it would be entirely arbitrary.</p>

<hr>

<p>As an interesting aside, the Isle of Harris in Scotland is not only not an island (there's an isthmus connecting part of it to a larger landmass) but even the isthmus part is not used to define the limit of the island, which occurs at some seemingly arbitrary point on the larger landmass! (see the map in the link to see what I mean)</p>

<p><a href="https://en.wikipedia.org/wiki/Harris,_Scotland" rel="nofollow">https://en.wikipedia.org/wiki/Harris,_Scotland</a></p>

CC BY-SA 3.0
2015-09-26T06:20:11.607Z
Yeah, the Harris/Lewis divide is a (largely historical) political one, not a geographical one. It has little to do with the isthmus that separates part of Harris from the rest, but if I recall correctly the border does mostly run along a mountain ridge.
Semidiurnal Simon
CC BY-SA 3.0
2015-09-20T13:40:04.687Z
2015-09-20T13:40:04.687Z
decvalts
<p>I'm currently on holiday in Indonesia. In my travel guide I was reading about the island Samosir, which I'm visiting in a few days. I read that the island, which is located in lake Toba, is connected to the main island of Sumatra by an isthmus. This got me wondering whether this wouldn't technically make Samosir island a peninsula. </p>

<p>So my question is: what (if anything) is the technical difference between a peninsula and an island connected to its parent landmass by an isthmus?</p>

CC BY-SA 3.0
2016-02-25T00:46:52.537Z
When the tide goes out?
naught101
<land-surface><geomorphology>
When does an island with isthmus become a peninsula?
user34646
# When does an island with isthmus become a peninsula?

(Asked by: username_0 on 2015-09-16)

I'm currently on holiday in Indonesia. In my travel guide I was reading about the island Samosir, which I'm visiting in a few days. I read that the island, which is located in lake Toba, is connected to the main island of Sumatra by an isthmus. This got me wondering whether this wouldn't technically make Samosir island a peninsula.

So my question is: what (if anything) is the technical difference between a peninsula and an island connected to its parent landmass by an isthmus?

**Tags:** land-surface, geomorphology

> **Comments:**
> **username_1**: When the tide goes out?  

---

## 2 answers

### Answer by username_2 on 2015-09-26. Score: 2

In a topological sense, if it's connected by an isthmus then it isn't an island. That doesn't mean that it might not be called that - but the answer is a cultural & political one, and hence won't adhere to strict definitions.


---

### Answer by username_3 on 2015-09-20. Score: 2

I think the naming difference is largely qualitative and even arbitrary in some cases. There are lots of 'islands' that are technically connected to a larger landmass by an isthmus of some sort, which would make them peninsulas technically, and not islands.

If you take the definition of a peninsula to be a body of land surrounded by water on three sides, then yes, the island in question could technically be called a peninsula.

Local names of landforms are often linked to cultural or historic influences, just as much as they are to their technical description. There's no 'threshold' of isthmus-width (as far as I'm aware), where once crossed, a peninsula-like island becomes an island-like peninsula . If there was it would be entirely arbitrary.

---

As an interesting aside, the Isle of Harris in Scotland is not only not an island (there's an isthmus connecting part of it to a larger landmass) but even the isthmus part is not used to define the limit of the island, which occurs at some seemingly arbitrary point on the larger landmass! (see the map in the link to see what I mean)

<https://en.wikipedia.org/wiki/Harris,_Scotland>

> **Comments:**
> **username_2**: Yeah, the Harris/Lewis divide is a (largely historical) political one, not a geographical one. It has little to do with the isthmus that separates part of Harris from the rest, but if I recall correctly the border does mostly run along a mountain ridge.  

---

